The investigators enrolled 90 patients on maintenance hemodialysis with dialytic vintage ≥12 months, iPTH 150-300pg/ml and serum calcium<2.5mmol/L. Patients were randomized to three groups with different dialysate calcium concentration , 1.25 mmol/L(DCa1.25), 1.5mmol/L(DCa1.5) and 1.75 mmol/L(DCa1.75) for 24 months respectively. Hemodialysis was performed for 4 hours three times weekly. Serum total calcium(tCa), ionized calcium(iCa),intact parathyroid hormone(iPTH)and phosphorus (P) levels were recorded before and after the study and single dialysis session in every patient. iCa and P levels were measured in spent dialysate.Bone density, bone-specific alkaline phosphatase(BAP), osteoprotegerin(OPG)、β-crosslaps、total Procollagen Type I Intact Propeptide (P1NP）and vascular calcification were measured in every patient periodically. vascular calcification including aortic arch calcification, abdominal aorta calcification and coronary artery calcification were measured by chest radiography, lateral lumbar radiographs and coronary artery computer tomography (CT) respectively. The primary endpoints included death, cardio-cerebral vascular disease(defined as heart failure, myocardial infarction and stroke), newly nontraumatic bone fracture, secondary parathyroidism uncontrolled by medicine and valvular or vascular calcification. The secondary endpoint were admission or emergency observation.

Inclusion Criteria:

• Age 18-65, maintenance hemodialysis, dialytic vintage ≥12 months, iPTH 150-300pg/ml, serum calcium<2.5mmol/L, serum calcium<2.5mmol/L.

Exclusion Criteria:

• Age<18 or >65 Severe acid-base disturbance History of parathyroid glands or adrenal gland combined with consumptions or malnutrition anemia due to acute bleeding or other diseases except for renal failure newly occurred bone fracture within 3 months active stage of immunological diseases using glucocorticoid or immunosuppressor combined with any disease with expect duration <2 year newly occurred acute heart failure, acute myocardial failure , acute cerebral infarction or stroke within 6 months pregnant women of women in preparation for pregnancy