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Objective: To investigate the effect and its possible mechanism of interleukin-17 (IL-17) on invasion and metastasis of human colon cancer cells., Methods: IL-17 was added into the culture media of human colon cancer cells SW480 and LOVO. Cells were divided into 4 groups: SW480 control group (SW480 cells), LOVO control group (LOVO cells), SW480 experiment group (50 μg/L IL-17+SW480 cells), and LOVO experiment group (50 μg/L IL-17+LOVO cells). Cell growth was measured by CCK-8 assay. The proliferation rate(%)=[(Aexperiment group-Ablank)/(Acontrol group-Ablank)]×100%). The ability of cell invasion and migration was measured by transwell assay. Real time-PCR was used to detect mRNA expression of VEGF and MMP-9. Western blot was performed to detect protein expression of STAT3, p-STAT3, VEGF and MMP-9. Enzyme-linked immunosorbent assay (ELISA) was applied to measure the protein content of VEGF and MMP-9 in the supernatant., Results: After cultivation for 24, 48 and 72 hours, CCK-8 assay revealed that the proliferation rate of SW480 was 1.18%±0.07%, 1.42%±0.09%, and 1.62%±0.08%; the proliferation rate of LOVO was 1.13%±0.02%, 1.32%±0.05% and 1.73%±0.02% in experiment group. Transwell experiments showed that after cultivation with IL-17 for 24 hours, number of invasion cell in experimental groups (SW480: 34.00±0.45, LOVO: 41.60±0.51) was higher as compared to corresponding control groups (SW480: 4.53±0.14; LOVO: 3.67±0.33) with significant differences (SW480: t=-76.026, P=0.001; LOVO: t=-81.580, P=0.005). The number of migration cell in experimental groups (SW480: 36.40±0.51, LOVO: 46.40±0.68) was higher as compared to corresponding control groups (SW480: 7.83±0.69; LOVO: 6.67±0.48) with significant differences (SW480: t=-51.542, P=0.003; LOVO: t=-49.265, P=0.005). Real-time PCR results revealed that after cultivation with IL-17 for 24 hours, VEGF and MMP-9 mRNA relative expression levels in experimental groups (SW480: VEGF:1.53±0.12, MMP-9: 2.44±0.23; LOVO: VEGF: 2.96±0.35, MMP-9: 3.38±0.55) were higher than those in control groups (both 1) with significant differences (VEGF: t=3.799, P=0.043; MMP-9: t=5.254, P=0.039). Western blot illustrated that after cultivation with IL-17 for 24 hours, STAT3, p-STAT3, VEGF and MMP-9 proteins relative expression levels in experimental groups were significantly higher that those in control groups (SW480:STAT3: t=3.233, P=0.023; p-STAT3: t=3.954, P=0.032; VEGF: t=3.201, P=0.025; MMP-9: t=3.154, P=0.029; LOVO: STAT3: t=3.788, P=0.012; p-STAT3: t=2.662, P=0.040; VEGF: t=4.118, P=0.035; MMP-9: t=4.268, P=0.030). ELISA indicated that content of VEGF and MMP-9 in the supernatant of experimental groups (SW480: VEGF 5 491.41±63.22, MMP-9: 21.43±1.35. LOVO: VEGF: 8 631.46±129.59, MMP-9: 178.32±3.20) were higher than those in control groups (SW480: VEGF:4 456.32±87.56, MMP-9:18.57±2.44. LOVO: VEGF: 8 122.38±108.66, MMP-9: 163.22±6.89) with significant differences (SW480: VEGF: t=6.993, P=0.037; MMP-9: t=5.587, P=0.040. LOVO: VEGF: t=7.013, P=0.044; MMP-9: t=6.762, P=0.043)., Conclusion: IL-17 may be able to activate STAT3 signal transduction pathway in vitro through up-regulation of VEGF and MMP-9 expression, thereby enhancing the invasion and migration of colon cancer SW480 and LOVO cells.