Objective: To observe whether reactive oxygen species(ROS) is involved in large dose ketamine-induced apoptosis on cultured primary neuron. Methods: Neuronal culture media (C group), 1 mmol/L ketamine (K group) or 1 mmol/L ketamine combined with 2.5 μmol/L superoxide dismutase mimetic M40403 (M group) was applied to primary neuron at day 6 for 24 h. Intraneuronal ROS production, the percentage of apoptotic cells and pro-apoptotic protein Bax expression were measured. Results: ROS production, the percentage of apoptotic cells and Bax expression in K group were 1.7, 4.2, and 2.0-fold of those in C group, respectively(all P < 0.05). Compared with C group, M group had no statistically significant changes in ROS production, the percentage of apoptotic cells and Bax expression (all P > 0.05). Conclusion: ROS could mediate the apoptosis induced by large dose ketamine in cultured primary neuron.