Objective: To evaluate the effect and mechanism of laparoscopic sleeve gastrectomy (LSG) on the changes of sex hormone level in obese young men with acanthosis nigricans. Methods: The clinical data of 45 young male obesity patients [body mass index (BMI) = 30kg / m2] who underwent LSG was collected. The obesity patients were divided into obesity without acanthosis nigricans group (OB group, n=23) and obesity with acanthosis nigricans group (group AN, n=22). The anthropometries parameters(weight，BMI，waist circumference, body fat percentage and %EWL)，glucose metabolic indices[fasting plasma glucose (FPG)，fasting insulin(FINS)，glycosylated hemoglobin(HbAlc)，homeostasis model assessment—insulin resistance index(HOMA-IR)], lipid profile (TC, TG, HDL-C, LDL-C) and inflammatory factor (UA, TNFα) were evaluated and calculated. Changes of these variables before and after surgery were analyzed. This study was approved by the Ethics Committee of the Shanghai tenth people’s Hospital (ChiCTR-OCS-12002381). Results: Laparoscopic sleeve gastrectomy can significantly improve the level of total testosterone in obese young men. The total testosterone (TT) of the obese young men in the group AN was only 7.60 ± 4.43 nmol / L, which was lower than the normal level and significantly lower than that in the group OB (P < 0.01). The total testosterone (TT) of the OB group was 10.42 ± 5.14 nmol / L, which was also lower than the normal level. At 6 months after operation, the total testosterone levels of group OB and group AN were significantly higher than those before operation (P < 0.05). TT of group OB was 15.58 ± 5.32 nmol / L, and that of group AN was 21.13 ± 23.43 nmol / L. The total testosterone level of group AN was significantly higher than that of group OB (P < 0.05). TT in group OB and group AN were negatively correlated with BMI, fat%, HOMA-IR, fasting and 2-hour postprandial insulin (P < 0.05), but not correlated with fasting and 2-hour postprandial blood glucose (P > 0.05). Conclusion: Laparoscopic sleeve gastrectomy can not only effectively reduce the weight of obese patients, but also significantly improve the hypotestosterone of obese men with acanthosis nigricans by improving insulin resistance and inflammation.