Abstract: Advanced analysis code on fuel assembly homogenization, Sim FA, has been developed by CNPO to improve the accuracy of few group cross section generation for the further use in the core code embedded in full-scope NPP control room simulators. In this paper, the burnup calculation strategy adopted in Sim FA, i.e. the Extended Predictor-Corrector Method incorporating the Linear Rate Method is presented, with the emphasis on Gadolinium-bearing assembly case. In comparison with the conventional burnup calculation methods, Sim FA demonstrates a better performance considering both the calculation efficiency and accuracy. The burnup calculation strategy implemented in Sim FA enables a fairly accurate burnup calculation with sufficiently large step size, and is therefore considered as a suitable way for the gadolinium-bearing assembly burnup calculation.