Wide area information is easily lost and distorted caused by disturbance， which is not fully considered in current wide area protection principle. A wide area backup protection algorithm with high fault-tolerance performance is proposed to implement the centralized substation backup protection system（CSBPS）. CSBPS can locate the fault element with fault-tolerance judgment according to fault direction and fault distance information calculated with currents and voltages measured from electric elements of local substation and collected from the adjacent substations.The results of a case study show that no uncorrected judgment happens to CSBPS in case any one of protection elements mal-operates， fails to operate or loss of fault information. The proposed algorithm is simple and reliable with good fault-tolerance capability.