The invention provides a vehicle-mounted storage batter capacity monitoring method and apparatus. According to the monitoring method, a controller collects the internal resistance of a storage battery; the internal resistance is compared with a correspondence relation table of residual storage battery capacities and storage battery internal resistances to determine the residual capacity of the storage battery, wherein the correspondence relation table is stored in the controller in advance; and the residual capacity is sent to an instrument for displaying, thereby warning the driver. The cost is low; and a problem that the cost is high when a storage battery capacity sensor is used for monitoring the residual capacity of the storage batter can be effectively solved.