A novel principle of segregated phase impedance differential protection based on the fault components is proposed. The impedance differential criterion is created with the difference between two impedances which are calculated from fault component data at both ends of the line， respectively. By this principle， it is unnecessary to synchronize sampled data， and the influence of capacitive current and fault resistance can be ignored. The current amplitude differential criterion is proposed to supplement the impedance differential criterion. It takes the difference of two current amplitudes calculated at both ends as the operating component， and the sum of these two current amplitudes as the restraint component. The simulation results show the correctness and validity of the principle.