A stratified multistage whole-group unequal proportional random sampling method was used to select 1656 men over 50 years of age as study subjects, and the International Erectile Function Questionnaire (IIEF-5) score, Male Sexual Function Questionnaire (O’Leary 1995), International Prostate Symptom Score (IPSS), body mass index (BMI), and prostate volume were recorded, and previous history of diabetes mellitus, hypertension, hyperlipidemia, cardiovascular and cerebrovascular diseases, and usual smoking and alcohol consumption. The χ2 test and logistic regression analysis were applied. RESULTS: A total of 1644 study subjects met the criteria, and the overall prevalence of ED, hypoactive sexual desire and ejaculatory disorders were 90.45%, 60.04% and 38.81%, respectively. The differences in the prevalence of ED, hypoactive sexual desire and ejaculatory disorders among the age groups were statistically significant. The results of multifactorial analysis showed that age was associated with ED, hypoactive sexual desire and ejaculatory disorders, BMI was associated with ED, hypertension and prostate volume were risk factors for hypoactive sexual desire and ejaculatory disorders; alcohol consumption was associated with ejaculatory disorders. Conclusion: The prevalence of erectile dysfunction, low libido and ejaculatory dysfunction increased and decreased in men over 50 years old in Beijing, indicating that middle-aged and older men can have good ejaculatory function, and the inability to achieve good erection due to various factors is the main reason affecting sexual life.The prevalence of ED, low libido and ejaculatory dysfunction increased with age, and age is a common risk factor for all three.BMI is a risk factor for ED BMI is a risk factor for ED, hypertension and prostate volume are risk factors for low libido and ejaculatory disorders; alcohol consumption is associated with ejaculatory disorders. Male sexual dysfunction is manifested as abnormal libido, erectile dysfunction or abnormal erection, abnormal ejaculation, and sensory disorders, among which erectile dysfunction is the most important. Since male sexual dysfunction involves various disciplines, different diagnostic criteria and classification methods lead to different findings of epidemiology and risk factors. In this study, the International Questionnaire on Erectile Function (IIEF-5) and the Male Sexual Function Questionnaire (O’Leary 1995) were used to investigate the prevalence of sexual dysfunction (including hypoactive sexual desire, erectile dysfunction, and ejaculatory dysfunction) and related risk factors in men over 50 years old in Beijing. 1. Subjects and methods 1.1 Subjects This study used a multicenter prospective stratified multistage whole-group unequal proportion random sampling method, with streets as the main stratum and communities and administrative villages as the basic sampling units, and all communities and administrative villages constituted the overall sample. The streets were used as the main stratum, and the communities and administrative villages were used as the sub-strata. The study population was men ≥50 years old in the resident population of 15 communities in urban and suburban areas of Beijing as of June 1, 2008. Exclusion criteria: (1) those with previous history of prostate, urethra and bladder surgery; (2) those with neurological disorders that may affect urination and sexual function; (3) those with psychiatric disorders that cannot cooperate; (4) those with history of bladder and prostate tumors; (5) those with urethral strictures and those taking drugs that may affect sexual function; (6) those with significant genital system dysplasia, malformations, and idiosyncratic infections. 1.2 Investigations included: recording of International Erectile Function Questionnaire (IIEF-5) score, male sexual function questionnaire (O’Leary 1995), International Prostate Symptom Score (IPSS), body mass index (BMI), prostate volume (transabdominal ultrasound), previous history of diabetes, hypertension, hyperlipidemia, cardiovascular and cerebrovascular diseases, usual smoking and alcohol consumption The study was approved by the Ethics Committee. The study was discussed and approved by the ethics committee and all respondents signed the informed consent form. 1.3 Statistical methods SQL-Server was used to establish the database, randomization method was used by SAS6.0 software random table method, and the findings were analyzed by SPSS11.0 software. Continuous variables were expressed as X±SD, and median (quartiles) was applied for skewed distribution information. The χ2 test for comparison between multiple groups, P<0.05 was considered statistically significant, and logistic regression analysis was used for regression and correlation. 2. Results A total of 1656 subjects were investigated in this study, of which 1644 subjects met the inclusion criteria, with a mean age of 64.5±9.8 years (50-93 years). More than 50% of the subjects had smoked or were drinking alcohol, and 11.9% of the subjects were obese (BMI >27 kg/O). The most common concomitant disease was hypertension (31.6%), followed by hyperlipidemia (19.1%), and diabetes mellitus (12.1%).