The invention provides a method for testing self-discharge of a battery. The method is characterized by testing an SOC-OCV curve of batteries, presetting p% SOC and V0 in an interval in which an OCV changes a lot, testing battery relaxation time t under the p% SOC according to the p% SOC and the V0, testing an open circuit voltage attenuation rate at the standing time T under the preset p% SOC toobtain a self-discharge rate after the batteries are placed for the time t, and taking the self-discharge rate as a basis for selecting the self-discharge degree of the batteries and carrying out grading and matching on the batteries. According to the method, the influence of the SOC state on the battery self-discharge test result is considered, so that the screening result of the self-discharge batteries is more reliable; the influence of polarization is effectively reduced by means of low-current and high-temperature conditions in a constant-voltage stage; and the self-discharge batteries are graded and utilized in an echelon manner, thereby greatly improving the stability of the matched module.