Objective：To investigate the influence of melanocortin-4 receptor（MC4R） gene rs17782313 polymorphism on the weight-reducing effect of laparoscopic Roux-en-Y gastric bypass（LRYGB）. Methods：A retrospective analysis was performed for the clinical data of 81 patients with morbid obesity who were admitted to Shengjing Hospital of China Medical University from January 2011 to December 2013 and underwent LRYGB. Peripheral blood DNA was extracted，the target gene was amplified by PCR，and then direct sequencing was used to determine the genotype of rs17782313. According to the genotype，the patients were divided into risk gene group and non-risk gene group，and the two groups were compared in terms of the changes in metabolic indices，body mass index （BMI），and excess weight loss（EWL） after surgery. Results：The frequencies of TT，TC，and CC genotypes of rs17782313 were 50.62%（41 patients），35.80%（29 patients），and 13.58%（11 patients），respectively. There were no significant differences between the patients with different genotypes in body weight，BMI，blood lipids，fasting blood glucose，and glycosylated hemoglobin. The non-risk gene group had slightly greater reductions in BMI and EWL than the risk gene group at 6 and 12 months after surgery（BMI in female patients：P6 months=0.296，P12 months=0.179；EWL in female patients：P6 months=0.139，P12 months=0.094；BMI in male patients：P6 months=0.295，P12 months=0.072；EWL in male patients：P6 months=0.106，P12 months=0.077）. Conclusion：The patients who carry C allele（risk gene） in MC4R rs17792313 have a similar weight loss as those who do not carry this allele.