The invention provides a method for accumulating the aggregate capacitances of a smart meter capable of realizing bidirectional metering, which comprises the steps of accumulating forward and reverse aggregate capacitances, and accumulating the forward and reverse aggregate capacitances of each rate, wherein an energy register adopts a 'read/reset' mode. In the two steps above, only the integer arithmetic is used, but the digital accuracy and the accurate accumulation of aggregate capacitances can be guaranteed, and most of data processing can be completed only by using an addition or subtraction method. In case of applying the method to an MCU (micro-programmed control unit), the cost of metering devices can be reduced, and the calculation speed is faster; and the testing personnel can read the aggregate capacitance metered by an electric energy meter at any time, and compares the metered aggregate capacitance with a standard aggregate capacitance, thereby calculating a metering error. By using the method provided by the invention, the forward and reverse aggregate capacitances can be respectively accumulated according to the requirements of an electric power company, and the combined aggregate capacitance also can be calculated.