Abstract: Objective To investigate the expression of leptin and its receptor in human colon cancer, the relationship between their expression and clinicopathological parameters, and the impact of exogenous leptin on the proliferation and apoptosis of colon cancer cell line HT-29. Methods Flow cytometry was used to detect the expression of leptin and its receptor in human colon cancer. MTT assay and flow cytometry were used to detect exogenous leptin on the proliferation, apoptosis and cell cycle of colon cancer cell line HT-29. Results The expression of leptin in human colon cancer and normal intestinal mucosa were (80.30±1.83)% and (59.83±1.12)% (P<0.01); the expression of leptin receptor in human colon cancer and normal intestinal mucosa were (82.14±1.63)% and (65.21±1.45)% (P<0.05). There was no correlation between their expression and patient's age, gender, tumor differentiated degree, lymph node, distance metastasis or clinical stage (P＞0.05). Concentration of 50, 100 and 200ng/ml exogenous leptin had a growing role in stimulating the proliferation of colon cancer cell line HT-29 (P<0.05). Cells were accumulated in S phase (P<0.05), but there was no difference in the apoptosis of HT-29 cells (P＞0.05). Conclusion Leptin and its receptor may play an important role in human colon tumorgenesis through accelerating cell proliferation.