NGX6, a candidate of tumor suppressor genes, can inhibit the proliferation of colon cancer in vivo and in vitro. The uncontrolled proliferation of tumor cell closely related with the dysfunction of the cell cycle. Flow cytometry and Western blot were used to explore effects of NGX6 on cell cycle progression and the expression of cyclins, CKI(p27,p16) in colon cancer cell line HT-29. Flow cytometry (FCM) showed that the overexpression of NGX6 increased the proportion of HT-29 cells at G0/G1 phase and decreased that at S, G2 and M phase. Western blot and FCM indicated that NGX6 could down-regulate the expression of cyclin E, cyclin D1 and increase the p27 expression,while NGX6 has no significant effect on expression of cyclin A and cyclin B. The expression of p16 was not detected in all groups. These results demonstrated that NGX6 arrested cell cycle progression at G0/G1 phase by down-regulating the expression of cyclin E, cyclin D1 and up-regulating that of p27 to inhibit the proliferation of HT-29 cells.