【Abstract】Objective To evaluate the clinical efficiency of online clearance measurement (OCM) based on conductivity variation. Methods Kt／V were assessed both by OCM and urea kinetic model in 38 maintenance hemodialysis patients, of which 2 groups were separated according to their residual renal function. Results Kt／V as estimated by OCM were 1.13±0.58, whereas measurements of Kt／V were 1.18±0.17 by urea kinetic model. They showed highly significant linear correlation(r=0.887，P＜0.01). Measurements of Kt／V by urea kinetic model had significant differences between 2 groups（P＜0.05), while Kt／V as estimated by OCM had no significant differences（P＞0.05）. Conclusion The OCM option of the hemodialysis machine provides an accurate tool for online monitoring of urea clearance to evaluate dialysis adequacy. 