Abstract: OBJECTIVE To study the relationship between CYP2C19 genetic polymorphism and blood concentration of mood stabilizer of valproic acid in schizophrenia patients. METHODS Schizophrenia patients treated with olanzapine and mood stabilizer of valproic acid were recruited based on the criteria of inclusion and exclusion. The blood samples were collected for the determinations of CYP2C19 genetic polymorphism and blood concentration of valproic acid. Then the blood concentration of valproic acid within the types of CYP2C19 genetic polymorphism was compared. RESULTS Blood concentration of valproic acid in the types of *2/*2 (122.06±41.30)mg·L^-1 and *2/*3 (132.34±51.34)mg·L^-1 were obviously higher than that of the wild *1/*1 type(79.41±25.14)mg·L^-1 (P<0.05, P<0.01). However, it was not significantly different in the types of *1/*1, *1/*2 and *1/*3 or in the types of *2/*2 and *2/*3. PM type (122.13±42.85)mg·L^-1 had obviously higher blood concentration than EM type(80.59±48.60)mg·L^-1(P<0.05). CONCLUSION The CYP2C19 types of *2/*2 and *2/*3 had high blood concentrations of valproic acid. These patients should receive a low dose of mood stabilizer of valproic acid in the treatment of schizophrenia.