【Abstract】 Objective To investigate the effect of different concentrations of sodium valproate on toxic reaction in children with epilepsy. Methods The clinical data of 128 children with epilepsy treated with sodium valproate in our hospital from May 2014 to June 2017 were retrospectively analyzed. High performance liquid chromatography was used to monitor the concentration of sodium valproate in serum. Children were divided into three groups according to different concentration, with 59 cases＜50μmol / mL in group A, 60 cases 50100μmol / mL in group B, 9 cases＞100μmol / mL in group C. The clinical efficacy and toxic reaction of each group were analyzed. Results The three groups with different concentrations of sodium valproate showed significant differences in the clinical efficacy (P＜ 001). The total effective rate of group B was significantly higher than that in other two groups (P＜ 005). The abnormal rates of liver function indexes (ALT, AST, GGT and TP) and renal function indexes (BUN, SCr) in group C were significantly higher than those in the other two groups ( P＜ 005). The incidence of other adverse reactions in group C was higher than that group A and group B, in which group B was significantly higher than group A, with a significant difference (P＜ 005). Conclusion Different plasma concentrations of sodium valproate have a certain impact on the treatment of children with epilepsy, and high plasma sodium valproate will increase the incidence of toxic reactions. Regular monitoring of serum concentration of sodium valproate is needed to reduce the risk of toxic reactions and improve the curative effect.