Abstract: The present disclosure provides a method for diagnosing an internal short circuit of a battery based on a relaxation voltage, including: 1) acquiring a relaxation voltage curve of each cell in a battery after a current is unloaded under same conditions of the battery; 2) extracting features from the relaxation voltage curve of each cell to obtain corresponding curve features; and 3) determining whether the internal short circuit occurs in the cell according to curve features, thereby completing diagnosis. The present disclosure has the advantages of short detection time and high accuracy over the prior art.