Objective To study CYP2C19*2 and *3 genotype with peptic ulcer patients using omeprazole in order to confirm therapeutic effect on CYP2C19 genotype with omeprazole whether there is a clear correlation and to guide clinical drug use. Methods 200 patients with gastroduodenal ulcer disease from Beijing outskirts secondary hospital were recruited, genomic DNA quick extraction kit and realtime-polymerase chain reaction (PCR) were used,the family of CYP450 gene polymorphism of metabolic enzymes was analyzed,ABI7500fas type fluorescent quantitative PCR was employed.Six genotypes of the P450 were analyzed , direct counting method was used to calculate the mutation genotype frequency and allele frequency. Hardy Weinberg of genotype distribution law was used to examine alignment and the presence of gender differences between genotypes and alleles mutation frequency difference by chi-square test. Results The effect of omeprazole treating gastroduodenal ulcer coincides with its genotype, the effect of omeprazole in patients with slow metabolism and pH increase time were remarkably better than patients with quick metabolism. Conclusions P450 family metabolic enzymes of the Han people in suburb Beijing have gene polymorphisms,but no gender differences between three types of gene.There exists obvious difference in the white European gene mutation frequency, and in CYP3A4*18 the homozygous mutations are not detected , 3A4*18 gene is not the main factor of 3A4 enzyme activity change. Omeprazole treatment effect is consistent with its genotype, CYP450 2C19 genotype is an important factor affecting the effects of omeprazole.