The invention discloses a method for improving current differential protection motion performance of a series compensated line. The method comprises the steps that S1, after the series compensated line goes wrong and current differential protection is started, a first fault current and a second fault current on two sides of a fault point of the series compensated line are collected; whether the first fault current and the second fault current meet a protection criterion is judged, and if yes, current differential protection motions are conducted, and a circuit breaker trips; if not, the current differential protection motions are not conducted. According to the method, By the adoption of the protection criterion, when a system operates normally and alternatively external faults occur, the amplitudes of the currents on the two sides of the line are close to each other, the motion increment of the portion is close to zero, and the false action risk cannot be increased; when internal faults occur, because faults of current reversal of the series compensated line are all faults of fault points close to a series compensated installation position, the difference between the amplitudes of fault currents on the two sides is large, so that the motion increment of the portion can effectively increase the motion quantity, protection motion sensitivity is improved, the motion rejection risk is lowered effectively, and protection reliability is improved substantially.