Abstract： Objective To evaluate the association of the C242T polymorphism in p22phox gene of NAD(P)H oxidase with type 2 diabetes mellitus （T2DM）in Han versus Korean population in Yanbian district of China and to observe C242T polymorphism characters of p22phox gene of NAD(P)H oxidase in T2DM patients with atherosclerosis. Methods Han and Korean nationality subgroups suffering from and not suffering from T2DM, with and without carotid atherosclerosis were enrolled and analyzed. The NAD(P)H oxidase P22phox C242T polymorphism was assayed by PCR-RFLP. Results In normal control group, there was no significant difference in the NAD(P)H oxidase P22phox C242T genotype distribution between Han and Korea nationality.In T2DM group, there was significant difference in the NAD(P)H oxidase P22phox C242T genotype distribution between Han and Korea nationality.In T2DM patients of Han nationality, there was significant difference in the genotype distribution of CC and CT+TT between patients with and without carotid atherosclerosis. Conclusions 1.There is a significant genotype difference in p22phox gene of NAD(P)H oxidase in T2DM patients between Han population and Korea population in Yanbian district. 2.T allele gene is a protective gene which can prevent against carotid atherosclerosis in T2DM patients of Han population in Yanbian district.