Abstract: Objective To exam the serum level of parathyroid hormone（PTH）in elderly isolated systolic hypertension（ISH）and explore how it is related to blood pressure and aortic stiffness. Methods A total of 101elderly outpatients and inpatients with ISH form Jiangxi Provincial People’s Hospital,69age-matched controls and 37middleaged controls were recruited between July,2009and July,2010. The levels of blood lipids,hepatic and renal function,and serum levels of calcium and phosphorus were measured by fully automatic biochemical analyzer. Brachial-ankle pulse wave velocity（baPWV）was detected by arteriosclerosis automatic measuring instrument. Serum levels of PTH and 25hydroxy vitamin D 25（OH）Dwere measured by radioimmunoassay. The baPWV and serum levels of PTH and 25（OH）D,along with the relevance of PTH to systolic pressure and baPWV,were analyzed in three groups. Results Among the ISH subjects,the elderly controls and the middle-aged controls,PTH levels were（53.7±23.4）,（42.0±15.1）,and（28.4±7.9）μg/L（P＜0.05）,respectively. Besides,baPWV for each group was（1926±332）,（1552±145）,and（1207±90）cm/s（P＜0.05）,respectively,and the serum levels of 25（OH）D were（11.8±8.3）,（17.2±7.0）,and（30.5±9.1）μg/L（P＜0.05）,respectively.Linear correlation analysis showed that PTH was positively correlated with age（r=0.251,P＜0.01）,systolic blood pressure（r=0.216,P＜0.01）and baPWV（r=0.264,P＜0.01）,respectively. Multiple stepwise linear regression analysis showed that after the adjustment for blood lipid level,body mass index and serum level of calcium and phosphorus, age,PTH level and 25（OH）D level were independent risk factors of systolic blood pressure（β=0.267,0.239,and-0.197,respectively;all P＜0.01）,age and PTH level were independent risk factors of baPWV（β=0.550,0.238,all P＜0.01）. Conclusion The serum level of PTH,systolic blood pressure and aortic stiffness increase with age.PTH may be involved in the pathogenesis of elderly ISH.