The invention provides an electrochemical mechanism modeling method for a lithium-ion battery, belongs to the field of batteries, and relates to a modeling method for the lithium-ion battery. The object of the invention is to rebuild an electrochemical mechanism modeling method for the lithium-ion battery by the adoption of a difference method for building a battery average value model based on an electrochemical mechanism model of the lithium-ion battery. The method includes steps: firstly, simplifying the mechanism model of the battery and building an average value model of the lithium-ion battery; secondly, identifying model parameters; and thirdly, obtaining the electrochemical average value model of the lithium-ion battery by the integration of identification parameters and known parameters. According to the method, the model calculation amount is less, the realization of a real vehicle is easy, and the method can be used for battery charge state estimation and health management and provide reference data for the operation of the battery.