Abstract: 【Abstract】Objective To establish the calcium supplement equation based on the two-stage calcium supplement model in order to promote the local citrate anticoagulation method simply and effectively used in clinical practice. Methods Fifty patients with renal replacement therapy were recruited in this study. They were effectively treated with continuous venous-venous hemofiltration under regional citrate anticoagulation (RCACVVH) for a total of 156 times. The CVVH adopted pre-dilution mode using the low-base and calcium-free replacement solution with the speed of 4L/h and lasted 6-8 hours. The anticoagulant citrate dextrose solution-a (ACD-a) was infused in arterial end, and the citrate was fed at 4.0～4.5 mmol/L plasma flow. The venous end was supplemented with 5% calcium chloride, and the calcium supplement rate was calculated by the "twostage calcium supplement model". The degree of coagulation in filter was observed during CVVH treatment. The calcium ion level at the arterial end and before the filter was measured by the iState biochemical analyzer every 2～3 hours, and the total calcium level was measured at the arterial end. The ratio of total calcium/ion calcium was then calculated. Results In the 156 times of CVVH, the percentage of effective anticoagulation using RCA was 96.79% (151/156), which is the ideal result. The calcium ion concentration of 0.2～0.4 mmol/L in ore-filter was found in 90.4% CVVH sessions, which approaches the target range. The calcium ion concentration of 1～1.2 mmol/L in arterial port was found in 90.5% CVVH sessions. The ratio of total calcium/ion calcium in the body was <2.5, without citrate accumulation. Skilled application of the two-stage calcium supplement equation can significantly reduce the frequency of calcium ion monitoring, and save the manpower, material and financial resources. Conclusions The two-stage calcium supplement model is effective, safe and simple. It is useful in hemodialysis.