Objective To investigate the effects of metformin on the migration and invasion abilities of PC-3 human prostate cancer cells in vitro and its possible mechanism. Methods PC-3 prostate cancer cells were cultivated by metformin hydrochloride at different concentrations(0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0 mg/mL) for 24 hours. MTT method was used to select the optimal drug dose. The 3.0 mg/mL metformin hydrochloride was used as the experimental drug dose(the observation group), and the control group that did not receive drug treatment was set up. MTT method was used to detect the proliferation of cells in each group at 24, 48, and 72 h. The other PC-3 prostate cancer cells were cultivated by cell culture medium contain 0, 3.0, 6.0, 3.0 mg/mL metformin hydrochloride(taken as the CK, MET1, MET2, MET3 groups) in 37 °C constant temperature box. The cell scratch test and Transwell test were used to test the cell migration and invasion;Western blotting was used to detect the expression of matrix metalloproteinase-2(MMP-2), matrix metalloproteinase-9(MMP-9), human glucose transporter 1(Glut1) and matrix metalloproteinase-14(MMP-14 or MT1-MMP) of cells in each group at 48 h after cell culture. Results PC-3 prostate cancer cells were cultivated by metformin hydrochloride at different concentrations for 24 h, and the proliferation of cells decreased with the increase of drug dose(P<0.05). Compared with the control group, the OD values of the cells in the observation group were low at 24, 48, and 72 h(P<0.05). At 0 h after scratch text, there was no obvious abnormality on comparison of the proportion of no cell region in the four groups(CK, MET1, MET2 and MET3)(P>0.05);at 24 and 48 h after scratch text, there was abnormality on comparison of the proportion of no cell region in the four groups(P<0.05). Significant difference was found in the proportion of no cells between the CK and MET1 groups at 24 and 48 h after scratch text(P<0.05). The migration index of the CK group was greater than that of MET1 and MET2 groups at 24 and 48 h after scratch text(P<0.05). At 48 h after scratch text, the migration index of the MET2 group was lower than that of MET1 group(P<0.05). The migration index of the MET3 group was negative. The number of invasive cells was in the following order:MET1