In this paper, a new type of high specific energy ratio power storage element supercapacitor battery is studied. In order to accurately estimate the state of charge of the battery, based on the in-depth analysis of the working principle of the supercapacitor battery, an equivalent circuit model describing the charging and discharging characteristics and relaxation characteristics of the supercapacitor battery is proposed and established. Firstly, the components of supercapacitor battery are modeled respectively. Then the overall equivalent model is constructed. Secondly, the identification method of equivalent model parameters is discussed, and the online identification method of recursive least squares (RLS) is used for parameter identification. The supercapacitor battery was tested on the charging and discharging experimental platform according to relevant standards. Finally, the established model is built and simulated in Matlab/Simulink using experimental data.