Objective: To investigate the effects of interleukin 1α (IL-1α) and its receptor antagonist (IL-1ra) on the proliferation and invasion of human colon cancer cells with different metastatic potentials as well as the role of IL-1α and IL-1ra in metastatic process. Methods: The colonic carcinoma cell lines with high liver metastatic potential (WiDr) and low liver metastatic potential (Caco-2 and Colo-320) were used. The gene and protein expressions of IL-1α and its type I receptor (IL-1R I) were determined by RT-PCR and ELSIA assay, respectively. After exposure to different concentrations of the exogenous IL-1α and IL-1ra, the cell proliferation of the three cell lines was measured by WST-1 assay and the invasive ability of WiDr and Caco-2 cells was assessed by using Transwell chamber. Results: The RT-PCR results showed that the IL-1α mRNA was only expressed in the WiDr cells of high liver metastatic potential but not in Caco-2 and Colo-320 cells of low liver metastatic potential, while the IL-1R I gene was expressed in all the three types of cells. The concentration of IL-1α protein detected in WiDr cells by ELISA assay was (7.85±0.52) pg/mL but was not detected in Caco-2 and Colo-320 cells. The exogenous IL-1α significantly increased the proliferative ability of Caco-2 and Colo-320 cells (all P<0.05), but had no effect on that of WiDr cells (P>0.05), while the exogenous IL-1ra markedly inhibited the proliferation of WiDr cells (P<0.05). The exogenous IL-1α significantly enhanced the invasive ability of Caco-2 cells (P<0.05), but had no influence on that of WiDr cells (P>0.05); the exogenous IL-1ra significantly inhibited the invasiveness of WiDr cells (P<0.05), but had no effect on Caco-2 cells (P>0.05). Conclusion: The liver metastatic potential of colon cancer is related to its IL-1α expression, and exogenous IL-1ra can inhibit the proliferative and invasive ability of colon cancer cells.