There are safety problems caused by thermal runaway in energy storage lithium-ion batteries. Thus an efficient method for simulating the internal temperature and pressure of a lithium-ion punch battery is developed, providing a real-time monitoring tool for battery status for energy storage systems. First, the processes of heat generation, gas production, heat transfer, and pouch expansion inside the battery are integrated into a unified evaluation framework by combining the chemical reaction, thermal circuit and self-expansion models. Secondly, a temperature/pressure evaluation model based on differential equations is established, in which the reaction and thermal circuit models are coupled through state parameters such as temperature and heat generation rate. Thirdly, the proposed method is applied to simulate the temperature and pressure of four samples. The comparison of the calculated and measured values shows that this method can efficiently calculate the internal temperature and pressure of the lithium-ion pouch batteries with a high accuracy with a maximum error of less than 4%. In addition, the solving process does not need to call on time-consuming coupled multi-physics simulations, and thus the efficiency is high.This work is supported by the Key Research & Development Project in Hunan Province (No. 2021GK2020).