An interface power control strategy based on power flow tracing and generator re-dispatch is presented. Power flow on the interface is firstly traced backward to the sending-end system to locate the generators to be adjusted. Then the power flow is traced forward to determine the loads affected in the receiving-end system. Power flow tracing is adopted again from such loads to determine their supplying generators in the receiving-end system， which is then used to compensate the load fluctuation according to the transmission change of the interface. Finally， New England 39-bus system and other systems are used to verify the effectiveness of the presented method.