Abstract: The electrochemical reaction in lithium-ion power battery is easily affected by temperature, which results in the variation of battery output power and capacity. In order to accurately estimate the internal temperature of the battery and provide a basis for battery management system, this study utilized electrochemical impedance spectroscopy to analyze the lithium-ion battery with different states of charge (SOC) and different states of health (SOH) under different temperatures. On this basis, an online estimation method for battery internal temperature based on electrochemical impedance spectroscopy was proposed. Results show that in a certain frequency band ranges from 10 to 1000Hz, the imaginary part of the impedance spectrum is not affected by SOC and SOH within the range of normal operating temperature (5~55℃). But it is sensitive to temperature change and can be used as the characteristic parameter of temperature evaluation. After that, according to the characterization of different electrochemical reactions at different frequencies, this study selected 10Hz and 100Hz as the excitation frequency of the battery internal temperature estimation. The internal relationship between the imaginary part of the battery impedance spectrum and the internal temperature was explored to effectively establish the internal temperature evaluation model of lithium-ion batteries. Finally, the verification test results show that the temperature evaluation model established in this study can control the temperature evaluation error within 1.58℃. This study shows that the imaginary part of the impedance spectrum has a good characterization ability for battery temperature, which can provide a reference for battery temperature control strategies and improve the temperature rise problem during battery operation.