PC12 cell line was used to examine the cytotoxicity of dopamine (DA). The higher dose of DA (400micromol/L) greatly reduced cell survival rate and induced apoptosis,meanwhile the lower dose (100micromol/L) had less cytotoxicity. Further studies showed that AMP (100micromol/L) were not cytotoxic at 24h, but decreased cell survival rae to 78% at 72h compared to control, and also exacerbate the cytotoxicity of DA (100micromol/L) at 72h. By determine the action of GSH level and SOD activity, we found that appropriate intracellular DA may be advantageous to protect cells from the toxicity of higher dose DA. The intracellular calcium concentration showed that DA's toxicity increased intracellular concentration of calcium. The results suggest that it was the extracellular DA that made cytotoxicity by decreasing cell's possibility of antioxide and increasing intracellular free calcium.