In recent years, the great progress has been achieved in the estimation of lithium battery state using the electrochemical impedance spectroscopy (EIS). In this paper, an EIS equivalent circuit model parameter extraction algorithm is proposed to analyze the battery equivalent circuit parameters in different states, which has advantages of simplicity and good convergence. Firstly, the initial values of equivalent circuit model parameters are obtained by combining the physical meaning of the model. The mapping relationship between the equivalent circuit and EIS is used for iteration to extract parameters. Compared with the theoretical reference value, the error of the key parameter is less than 4. 4% . To obtain the EIS data of lithium-ion battery under different states of charge, the electrochemical workstation is used to measure the EIS data of lithium-ion phosphate battery under constant temperature. Finally, by comparing the equivalent model parameters under different states of charge, the feasibility of using EIS to quickly estimate the state of lithium battery is verified to a certain degree.