Abstract: Objective To examine the relationship between the serum Klotho protein and hypertension in adults.Methods A cross-sectional study was conducted in Jinchang district of Suzhou city from January to May 2010.Subjects’ data on demographic,lifestyle,medical history,family history of hypertension,height,weight,waist and blood pressure was collected and levels of fasting blood glucose,serum uric acid,lipid levels,and microalbumin were checked. Based on the cross-sectional study,197 hypertensives and 197 normtensives were selected as research subjects using a 1∶1 matched case-control study,and serum Klotho level was tested in May 2016. The subjects were divided into four groups based on the quartile level of Klotho protein（＜206.48,206.48-290.48,209.49-430.27,＞430.27 ng/L）and the relationship between serum Klotho protein level and hypertension was analyzed by conditional Logistic regression analysis. Results Of 197 pairs of subjects,60 pairs were males and 137 pairs were females. The average age of all subjects was（51.7±8.7）years old. The median(P₂₅-P₇₅)serum Klotho protein level was 290.48（206.48-430.27）ng/L with the levels in hypertensives lower than in normotensives269.67（206.22-359.83）vs 313.95（218.46-483.39）ng/L,P=0.004. The univariate conditional Logistic regression showed that compared to subjects in highest quartile Klotho level group,subjects in the first,second and third quartile Klotho level groups had higher risk for hypertension with corresponding ORs（95% CI）of 2.46（1.40-4.31）,2.24（1.24-4.02）and 1.98（1.12-3.51）respectively. After adjustment of covariates including age,lifestyle,family history of hypertension,body mass index,fasting blood glucose,serum uric acid,lipid levels,and microalbumin,compared to subjects with the highest quartile Klotho group,ORs（95% CI）of hypertension in other three Klotho quartile groups were 2.01（1.08-3.71）,2.29（1.20-4.39）and 1.55（0.82-2.92）. Conclusion The low level of serum Klotho protein was positively correlated with risk of hypertension.