Thevenin second-order equivalent circuit model is used to describe the state space of the power battery with high accuracy and moderate identification difficulty. The DEKF+GA algorithm is proposed to identify the parameters of the equivalent circuit model of Li-ion battery with noise interference, and the GA algorithm is added to search for the optimal solution at the initial value of the DEKF solution to improve the accuracy and robustness of the DEKF algorithm. Experiments show that applying the DEKF+GA algorithm reduces the URMSE and UMAX by 29mV and 27.73mV respectively on average compared to the DEKF algorithm.