Urban mass transit system,conform alternating current(AC) to direct current(DC) through rectifiers,supply power to motor and vehiclel equipments,whose harmonics do harm to the safe and economic works of power system.In view of the characteristics of harmonic of urban mass transit system,simulation on adaptive neural network to detect and isolate the harmonics shows the results can be optimal with the moderate parameters.Simulation on the hybrid filter’s effective cooperation of active filter and passive filter shows this method can suppress the harmonics,improve and optimize power factor.