Objective To analyze the relationship between renal function impairement and obesity in patients with primary hypertension.Methods One hundred and twenty-eight primary hypertension patients with renal function impairement admitted to our hospital from January 2012 to December 2015 were divided into obesity group (n=68) and control group (n=60) according to the Asian obesity diagnosis criteria established by the International Diabetes Federation.Relationship of serum urea nitrogen (BUN),creatinine,cystatin C (Cys-C),urinary N-acetyl beta-D glucosaminidase (NAG),urinary micro albumin levels and BMI with renal function impairment in primary hypertension patients was analyzed by multivariate linear stepwise regression analysis.Results The BMI,serum levels of urinary NAG,Cys-C,BUN,and creatinine were significantly higher in obesity group than in control group (31.70±1.80 kg/m2 vs 23.95±2.00 kg/m2,19.34±1.40 U/L vs 14.92±1.31 U/L,0.69±0.06 mg/L vs 0.47±0.05 mg/L,11.50±2.90 mmol/L vs 8.60±1.90 mmol/L,159.50±10.40 μmol/L vs 148.90±10.70 μmol/L,P＜0.05).The incidence of urinary micro albumin was significantly higher in obesity group than in control group (79.4％ vs 46.7 ％,P＜ 0.01).Blood pressure,pulse pressure difference,BMI,fasting blood glucose,serum levels of ereatinine,urinary NAG,Cys-C,BUN and urinary micro albumin were the risk factors for renal function impairement in primary hypertension patients (P＜0.05,P＜0.01).Conclusion Renal function impairement is related with obesity in primary hypertension patients.