Lithium-ion batteries have become the main energy storage carriers in new energy vehicles, energy storage power stations and other systems by virtue of their high energy density, long cycle life, low self-discharge rate and many other advantages, but the characteristics of lithium-ion batteries’ structure and principle lead to the need for good monitoring and management for their safe and reliable use. Currently, most of the traditional lithium-ion battery condition monitoring methods are based on the characteristics of the external operating parameters of the battery, while electrochemical impedance spectroscopy is a method to study the state of lithium-ion batteries from the internal characterization, this study carries out the measurement experiments of the actual batteries on a time-domain impedance spectroscopy measurement system, traces the characteristics of impedance spectroscopy changes in different SOC (State Of Charge) and temperatures, and researches the relationship of the electrochemical impedance spectroscopy with the influence of the SOC and the temperature. The equivalent circuit model of lithium-ion impedance spectrum is constructed, the model parameters are fitted to the impedance spectrum data based on the ZView tool, and the joint estimation of lithium-ion battery SOC and temperature based on the time-domain impedance spectrum is realized by using the BP neural network estimation model with the model parameters as the inputs, and the lithium-ion battery temperature and SOC as the outputs, and none of the estimation errors is greater than 5%.