【Abstract】 Objective To evaluate the effect of calcium concentration in dialysate on serum ionized Ca (iCa), phosphate (P), intact parathyroid hormone (iPTH) and aldosterone (ALD) during hemodiafiltration (HDF) in chronic renal failure patients. Methods Sixty patients were assigned into 3 groups based on the calcium concentration in dialysate. Serum iCa, P, iPTH, ALD and blood pressure were measured before and after HDF session. Results In the group using Ca+2 1.25mmol/l in dialysate, iCa, P, ALD and blood pressure decreased significantly, and iPTH remained unchanged. In the group using Ca+2 1.5mmol/l in dialysate, iCa unchanged but P, iPTH and ALD decreased. In the group using Ca+2 1.75mmol/l in dialysate, iCa increased significantly but P, iPTH and ALD decreased. Conclusions Treatment with the addition of low calcium dialysate to hemodiafiltration is beneficial to reduce calcium load and serum ALD, to prevent iPTH from increase, and to decrease blood pressure.