To study single nucleotide polymorphisms (SNP) in A-922G, T-786C and G894T of endothelial nitric oxide synthase (NOS3) and to correlate the distribution of their allelic combinations with hypertension in Chinese Han nationality population, genomic DNA was isolated from venous blood leukocytes from 192 unrelated patients with hypertension (95 females and 97 males) and 122 healthy unrelated individuals (46 females and 76 males) as controls. SNPs of NOS3 A-922G, T-786C and G894T were genotyped by allele-specific primer (ASP) PCR. The distribution of genotype combinations of three SNPs was determined by clustering analysis. There were no difference in allele genotype distribution frequency and haplotype frequency of NOS3 G894T, NOS3 A-922G and NOS3 T-786C between the essential hypertension group and the healthy population (P>0.05). According to sex stratification, no association between essential hypertension and SNP of NOS3 A-922G,NOS3 T-786C or NOS3 G894T has been found in either the male subgroup or the female subgroup. In respect of allele genotype combination frequency in the natural distribution of NOS3 A-922 G, NOS3 T-786C and NOS3 G894T SNP, there was significant difference only in the allele genotype combination frequency of NOS3 G894G+A-922G+T-786T between the hypertension group and the healthy group (P<0.05, Chi2=4.5944). According to sex stratification, there were no significant difference in all above allele genotype combination frequency in three sites of NOS3 SNP between the hypertension male subgroup and the healthy male subgroup (P>0.05). There was significant difference in the allele combination frequency of NOS3 G894G +A-922G+T-786C between the hypertension female subgroup and the healthy female subgroup(P<001, Chi2=8.502). There was no association of SNP in NOS3 A-922G, NOS3 T-786C or NOS3 G894T with hypertension in the Chinese Han nationality population, nor was there a sex difference. The combination frequency of allele NOS3 G894G + A-922G + T-786C in the hypertension female subgroup was much lower than that in the healthy female subgroup, suggesting that female population with this combination genotype may be less susceptible to hypertension.