Objective To investigate the effects of melatonin on the changes of superoxide dismutase ( SOD ) , reactive oxygen species (ROS),and malondialdehyde(MDA) in N2A cells under hypoxia conditions.Methods Randomly divided the primary cultured neuroblasto-ma cells of mouse into the control group ,hypoxia group ,and MT treatment group .The MT treatment group were given melatonin 5μg/mL for 24 h to set up the treatment model .Rsbiotech of the hypoxia group and MT treatment group were given gaseous mixture of 95%N2 and 5%CO2 ,The ischemia hypoxia model of N 2A cells was set up with cells in the oxidative stress state and cultured for 24 hours at low concentra-tions of serum .The content of SOD , ROS, and MDA was measured respectively by xanthine oxidase , fluorogenic quantitative detection and thiobarbituric acid chromatometry .Results The expression of SOD in hypoxia group and MT treatment group were significantly decreased compared with that in control group(P<0.05).The level of SOD in MT treatment group significantly recovered compared with hypoxia group with singnificant difference (P<0.05).The expression of MDA and ROS in hypoxia group and MT treatment group were significantly in-creased compared with that in control group (P<0.05).The level of MDA and ROS in MT treatment group significantly recovered compared with hypoxia group with singnificant difference (P<0.05).Conclsion Melatonin provides a protective effect on the secondary damage of nerve cells with hypoxia ischemia .The possible mechanism is melatonin could play the role of free radical scavenging and up -regulate the ex-pression level of antioxidants .