Aluminum-sulfur battery with low cost, safety and high efficiency has potential for battery energy storage. Different from the traditional charging and discharging principle of lithium ion, aluminum ion and sodium ion battery, the charging and discharging process of aluminum sulfur battery is a multi-step continuous redox reaction. In this paper, the aluminum-sulfur battery equivalent circuit model based on second-order RC equivalent circuit was proposed, and the model parameters identification can be realized by using HPPC test data. Through the simulation test, the results show that the model has good accuracy under the condition of low current and medium current, which can meet the requirement of estimation of state of charge of aluminum-sulfur battery.