Objective: To characterize the effects of growth hormone (GH) on human colon cancer in vitro. Methods: Lovo cells were divided into control group and experimental groups and treated with different concentration of GH. MTT assay was used to determine the growth of the cells. The cell cycle and cell apoptosis of Lovo cells were detected by flow cytometer with PI and annexin V/PI double staining. Results: GH promoted the proliferation of Lovo cells, and the effects began at 12~24 h and peaked at 48 h. GH got the best effect on proliferation of Lovo cells when the concentration reached 200 ng/ml. After Lovo cells were treated by 200 ng/ml growth hormone for 24 h, the rate of G0/G1 stage decreased significantly, the rate of S stage increased significantly and the rate of G2/M stage increased slightly. For 72 h, the rate of G0/G1 stage decreased more significantly, the rate of S stage increased more significantly and the rate of G2/M stage increased significantly,the percentage of apoptotic cells also increased significantly. Conclusion: GH is a powerful promoter on proliferation of Lovo cells growth in culture. The effect of growth hormone manifesed a dose-dependent manner, and the saturation effect of growth hormone occurred at the concentration of 200 ng/ml, and its mechanism could be performed by promotion the cells G0/G1 stage to S and G2/M stage.