Abstract: NONMEM program was applied for estimating population pharmacokineticparameters of cyclosporin A(CsA).The influence of body weight,age,sex and drug administrationhistory on clearance were investigated.There were 281 CsA concentrations in whole blood from 60cl inical renal transplantation patients.Samples were analysed by HPLC and FPIA(TDx,Abbett,monoclonal antibod). One conipartment open model with first-order absorption and elimination was used to analyse thedata,Population mean values of CL(L·h^-1),Vd(L)and K_a(h^-1 )were 5,227,and 1.28respectively.The interindividual variations of CL,Vd,and Kawere 3.27%,29.01%,and75.10%respectively.The residual error was 31.19%。The adjustment value of weight to clearancewas 0.03 times with additional model.CL increased.3l in male l)atients,and decreased l2.7 whenpatients were treated with CsA for a long time.