The invention provides a battery module control method. A control main module is started up to perform polling on at least one battery charging-discharging secondary module to receive information of the battery charging-discharging secondary module which needs online charging and discharging; after the battery charging-discharging secondary module receives the polling information from the controlmain module, the battery charging-discharging secondary module responses the polling information and transmits a unique ID number in a processor thereof to the control main module; the control main module receives the unique ID number from the battery charging-discharging secondary module and appoints one unique control sequence number corresponding to the unique ID number and sends the unique control sequence number to the battery charging-discharging secondary module; and the battery charging-discharging secondary module receives and stores the unique control sequence number appointed by thecontrol main module, so that communication and positioning between the control main module and the battery charging-discharging secondary module can be performed conveniently. A communication methodis simple and easy to implement, and convenience in operation and high reliability are achieved; and the appointed unique control sequence number is adopted to replace a 29-bit ID communication control sequence number in the prior art, so that the bus data size is reduced, and communication efficiency is improved.