In order to study the mechanisms of inhibitory effects of manganese on neurocyte. PC12 cells were incubated in culture media with 100, 200 and 500 mmol/L manganese(MnCl2) for 24, 48 and 72 h respectively. MTT test, Trypan blue exclusion test, malondiadehyde(MDA) colorimetry and DNA gel electrophoresis were performed to exam proliferation, lipid peroxidation, and apoptosis of PC12 cells. The results of MTT test reveled that manganese (100-500 mmol/L) could inhibit the proliferation of PC12 cells. DNA gel electrophoresis showed that the apoptosis of the PC12 cells could be induced by manganese (100 mmol/L). It is concluded that manganese can inhibit proliferation of PC12 cells, the mechanism includes the interference of DNA metabolism, inhibitory of lipid peroxidation, and cell apoptosis.