Aim To study renin-angiotensin-aldosterone system (RAAS) hormone levels and CYP11B2－344C/T gene polymorphism in essential hypertension patients with obesity, discuss genetic susceptibility of CYP11B2－344C/T genotype and the correlation between susceptible gene and RAAS levels.Methods 60 cases of patiens with 1～2 grade essential hypertension (30 cases essential hypertension patients with obesity, 30 cases essential hypertension patients without obesity), and 60 people from the Examination Center (30 cases obesity people without hypertension, 30 cases healthy people) were enrolled randomly. CYP11B2－344C/T gene polymorphisms were analyzed using polymerase chain reaction-restriction fragment length polymorphism and agarose gel electrophoresis methods, plasma RAAS concentration were detected by radioimmunoassay.Results Multi-compared with number of cases of TT and TC＋ CC genotype, there were significant differences (P<0.05). And differences in essential hypertension with obesity group was the most significant multi-compared with the number of T and C alleles, significant differences were found (P<0.05), and differences in essential hypertension with obesity group was predominant. Plasma renin, angiotensin Ⅱ, aldosterone concentrations in genotype TT cases were much higher than those of TC and CC genotype (P<0.05), but there was no significant differences between CC and TC genotype cases (P>0.05).Conclusions In CYP11B2－344C/T gene polymorphism, TT genotype may be susceptible genotype of essential hypertension patients without obesity, and T allele may be susceptible one of them. Each component of plasma RAAS hormone levels in the TT genotype cases was significantly higher than the CC and the TC genotype ones.