Objective To observe the effect of bloodletting cupping on the serum insulin level in patients with simple obesity. Methods Fifty simple obesity patients were randomized into a treatment group and a control group, 25 in each group. The treatment group was intervened by bloodletting cupping, while the control group was by oral administration of Sibutramine Hydrochloride. The efficacy for losing weight and the serum insulin level were evaluated and compared before intervention and after 2 treatment courses. Results The total effective rate was 88.0%in the treatment group versus 80.0%in the control group, and the difference was statistically insignificant (P>0.05). The serum insulin levels were changed significantly in both groups after intervention (P＜0.05). After intervention, there was a significant difference in comparing the serum insulin level between the two groups (P＜0.05). Conclusion Bloodletting cupping can significantly improve the serum insulin level in patients with simple obesity.