Abstract: It is difficult to model the electric quantity parameters of lithium battery directly and it is not convenient to estimate the power supply parameters.This paper proposes a solution to model the state parameters of lithium battery based on EKF-UKF model algorithm directly. The battery model parameters obtained by EKF algorithm and UKF algorithm are applied to observe the charge state of lithium battery. In this way, the battery model parameters can be updated in real time while the battery quantity estimation is carried out, and the influence of drifting current on the estimation accuracy can be effectively reduced. The experimental results show that this compounding algorithm is low complexity, high accuracy and robustness, and can quickly estimate the parameters of lithium battery.