The invention discloses an electric energy meter combination error testing method. The method comprises the steps that the sharp electric energy, the peak electric energy, the flat electric energy, the valley electric energy and the total electric energy of an electric energy meter are acquired respectively, and a register combination error is calculated. The electric energy meter combination error testing system provided by the invention is used for testing the electric energy register combination error, and is mainly used for calibrating the multi-rate measurement function of the multi-function electric energy meter and the error between the measurement of each period and an electric energy indicating value, wherein the error between the electric energy values should not exceed +/-0.1%. Under a reference condition, the energization word display of the measured meter is more than 100KW, and continuous word display is not less than 120 hours. During energization, sharp, peak, flat and valley periods are required to alternate arbitrarily within every 24 hours, and switch more than 7 times every 24 hours. PC software reads the electric energy values of sharp, peak, flat and valley periods and the total electric energy value of each measured meter through a 485 communication port, and then carries out calculation according to a formula.