The possible causes of blood in urine after sexual intercourse are as follows: 1. The presence of urinary system-related lesions themselves, such as the presence of urethritis, glansitis or cystitis and other diseases that cause bacterial contamination during sexual intercourse, and the presence of related sexually transmitted diseases that lead to increased mucosal congestion and edema. In this case, the condition of hematuria after sexual activity can appear, mostly accompanied by urinary frequency, urinary urgency, painful urination, back pain, fever and other symptoms, and it is necessary to conduct routine urine examination and urine culture test to confirm the diagnosis. After the diagnosis is made, anti-infection treatment should be actively carried out, and sexual life should be avoided during the treatment period. 2. The bleeding is caused by damage to the local mucosa due to overly violent actions during sexual life. This condition is usually not accompanied by abnormal urination, and mostly occurs after too violent sexual life. It is necessary to drink more water, urinate more and abstain from sex, and the symptoms can be relieved by themselves after moderate rest, without the use of medication.