Abstract: Tacrolimus is commonly used in the treatment for the refractory primary nephrotic syndrome (PNS) in the pediatric patients. Data were retrospectively obtained from 100 children with 357 tacrolimus trough concentrations in our center between May 2010 and March 2016. Information of age, sex, body weight, drug dose, co-therapy medications, laboratory tests and sampling time were collected. The population pharmacokinetic model was developed using nonlinear mixed effect modeling (NONMEM) software. A one-compartment model with first-order absorption and elimination best described the data. The population estimate of apparent clearance (CL/F) and apparent volume of distribution (V/F) was 6.54 L·h^-1 and 86.2 L, respectively. Body weight (WT, kg), daily dose of tacrolimus (DD, mg·day^-1) and co-therapy azole antifungal agent have a significant impact on the CL/F. The final PPK model of CL/F was:CL/F=6.54×((WT)/25)^K×((DD)/1.5)^0.293×0.657^Azole,K=(WT^-30.9)/(WT^-30.9+10.4^-30.9). When combined with azole antifungal agents, Azole was 1, whereas vice versa was 0. This is the first PPK study of tacrolimus conducted in pediatric patients with PNS, which may facilitate individualized drug therapy of tacrolimus.