Mr. Li is usually optimistic and open-minded, broad-minded and fat, with a height of 1.81 meters and a weight of 126 kilograms. Recently, Mr. Li encountered a troublesome thing: married for 2 years, his wife has not been pregnant, to the hospital, a semen examination, found to be a serious oligospermia: sperm density of only 1.6 × 106 / ml, forward movement of 6%. Mr. Li thought his health had always been good, but he did not expect that his semen quality was not up to standard. We combined Mr. Li’s other test results and analyzed that this condition was related to him being too fat. Body mass index (weight in kilograms divided by height in meters squared) is a measure of the degree of fat and thinness of the human body and whether the health of a standard, the normal body mass index of 18.5 ~ 25%, more than 30% is obese, and Mr. Li is 38.6%, belonging to the severe obesity. Obesity is one of the factors leading to male infertility, the reasons are as follows: 1, obese people have too much body fat, will produce too much aromatase, resulting in increased levels of estrogen in the body, thus negative feedback inhibition of the hypothalamus pituitary, so that the body’s testosterone levels decline, resulting in sperm production is affected; 2, obesity can lead to hypertension, high blood sugar, high blood fat, that is, metabolic syndrome, and now research shows that the Metabolic syndrome will affect male gonadal function, leading to sperm production disorder; 3, obesity will also affect male libido and sexual function, such as leading to male erectile dysfunction or ejaculation disorders, thus affecting male fertility; 4, obese people are often accompanied by sleep apnea, leading to lack of oxygen in the body, affecting the sperm production and vitality. The treatment of infertility caused by obesity factors is firstly to correct lifestyle and reduce weight. It has been reported that after weight loss, obese men’s semen volume, total sperm count and blood testosterone level have been improved. For obese patients with sleep apnea, a suspensory-palato-pharyngeal plasty can be used to improve the hypoxic state of the organism. Medication is also a means of treating obese infertility. For patients with elevated estrogen, aromatase inhibitors such as letrozole can lower estrogen and raise testosterone levels; if estrogen levels are normal, gonadotropin therapy can be used. For erectile dysfunction caused by obesity, treatment with phosphodiesterase inhibitors can achieve good results. In addition, metformin helps to reduce body weight, reduce insulin resistance, increase testosterone levels, and has an improved effect on semen quality in obese patients. For patients for whom the above treatments are ineffective, assisted reproductive techniques such as artificial insemination, in vitro fertilization-embryo transfer, and monosperm follicular plasmapheresis are the last resort for patients with oligozoospermic infertility. Many studies have shown that human semen quality is on a downward trend, and besides the effects of environmental pollution and life stress, more and more people are becoming obese as one of the reasons. Therefore, controlling obesity is not only to prevent chronic diseases, but also an important means to maintain male vigor and virility.