The power battery system is the core for electric vehicles, which is composed by hundreds or thousands of cells in series and parallel generally. Cells have inherent inconsistency because of slight deviations and uncertain factors in their production process. And they work in the complicated charge and discharge environment for a long time, so their inconsistency will be further aggravated to greatly reduce the available capacity and shorten the service life. There is an urgent need to establish an evaluation mechanism for the inconsistency of batteries to provide the gist for the high-efficiency and reliable management. The test platform and scheme are built to obtain accurate data. And a comprehensive evaluation method for battery inconsistency is proposed based on the information entropy. Taking the capacity, internal resistance and the ratio of constant current charge capacity to constant voltage charge capacity as evaluation factors, the inconsistency of the battery pack composed of twelve cells is analyzed comprehensively. Experimental results show that the method can scientifically evaluate the inconsistency of the battery pack in different life and has wide adaptability.