The problem appears when traveling-wave differential protection was used to series compensated transmission line. Although the impedance uniformity of transmission line is broken by the f ixed compensated capacitor (FSC), the line between the relay location and FSC is uniform transmission line. The traveling-wave equation is applicable in the transmission line between relay location and FSC. Based on the previous analysis, an advanced traveling-wave differential protection was proposed for series compensated transmission line and also the method to calculate the differential current of fault phase and healthy phase are extended. When external fault or internal fault on FSC mounting point occurs, in principle, this method can completely eliminate the influence of capacitor current, which satisfies the requirement of sensitivity and security. Elector-Magnetic Transient Program (EMTP) simulations demonstrated it.