In order to study the effect of exercise combined with diet intervention on immune function of patients with severe obesity, 20 patients with severe obesity were randomly divided into experimental group and control group. For experimental group, exercise combined diet intervention was carried out, while the control group did not receive any intervention. The changes of basic indices, cellular immune indices, immunoglobulin, IL-2 level, IFN-gamma level, NK cell and LAK cell of the two groups were measured. The results showed that the waist circumference, waist-hip ratio, body mass and BMI of obese patients were significantly decreased, CD4+/CD8+ was significantly increased, IgG was significantly increased, serum levels of IL-2 and IFN-gamma were significantly increased, and killing activity of NK cells and LAK cells was increased. It shows that exercise combined with dietary intervention can slow down the decline of immune function in patients with severe obesity.