Objective To investigate the correlation between CYP2C19 gene polymorphism and olanzapine-induced sinus tachycardia. Methods A total of 241 patients with schizophrenia who were treated with olanzapine alone after admission were selected, including 119 patients with sinus tachycardia( tachycardia group) and 122 patients without sinus tachycardia( non-tachycardia group). Detection and typing of SNP loci rs4244285, rs4986893 and rs12248560 on CYP2C19 gene were carried out, and the genotype and allele distribution between the two groups were analyzed and compared. Results There were no significant differences in gender, age, course of disease and medication between the two groups( P>0.05). There were no significant differences in the distribution of gene frequency and allele frequency between the two groups( P>0.05). Among 3 gene loci, the distribution frequency of *1/*3 in tachycardia group was lower than that in non-tachycardia group[ *1/*1 in tachycardia group( n=46,38.6%) and non-tachycardia group( n=38,31.1%); *1/*3 in tachycardia group( n=9,7.6%), non-tachycardia group( n=19,15.6%), 95%CI=0. 159-0.964, χ2=4.299, P< 0.05], and the difference was statistically significant. * 1/*17 was not detected in tachycardia group, and the distribution frequency was lower than that in non-tachycardia group,[ *1/*1 in tachycardia group( n=46,38.6%) and non-tachycardia group( n=38,31.1%); *1/*17 in tachycardia group( n=0,0) and non-tachycardia group( n=4,3.3%), P < 0.05], and the difference was statistically significant. Ultrarapid metabolizer( UM) was not detected in tachycardia group, and its distribution frequency was lower than that in non-tachycardia group,[ extensive metabolizer( EM)( n=46,38.6%), non-tachycardia group( n=38,31.1%); *1/*17 tachycardia group( n=0,0), non-tachycardia group( n=4,3.3%), P<0.05], and the difference was statistically significant. Conclusions *1/*3 and *1/*17 on CYP2C19 gene may reduce the risk of sinus tachycardia after olanzapine administration, and CYP2C19 may be related to olanzapine-induced sinus tachycardia.