In order to improve the accuracy of dynamic capability measurement of Li ion battery,a single chip microcomputer system was used to process the collected loop current and terminal voltage,and the electromotive force and internal resistance were obtained based on the least square method.Experimental data show that the electromotive force is not linearly related to the state of charge (SOC),but the linear processing method is still available in a small interval.Because of the chemical characteristics of Li ion battery,there will be a large measure error at different temperatures.Along with the aging of Li ion battery,the internal resistance also affects the result obviously.Considering the temperature compensation and aging correction,the measurement result was corrected.