A power transmission system for a vehicle, comprising: an engine unit configured to generate power; a dual clutch, wherein the engine unit is coupled with an input terminal of the dual clutch; a transmission unit adapted to selectively couple with the engine unit, and configured to transmit the power generated by the engine unit, the transmission unit comprising a first input shaft and a second input shaft, wherein the second input shaft is coaxially fitted over the first input shaft, the first input shaft is coupled with a first output terminal of the dual clutch, and the second input shaft is coupled with a second output terminal of the dual clutch, each of the first input shaft and the second input shaft is provided with one fixed driving gear; an output unit configured to transmit the power output by the transmission unit; a first motor generator coupled with the one driving gear on the second input shaft via an intermediate gear (411, 44, 451, 452), wherein the engine unit and the first motor generator are configured to drive the front wheels; an output shaft, provided with two driven gears, wherein the two driven gears are configured to mesh with the driving gears on the first input shaft and the second input shaft, to form two gears; a synchronizer, disposed on the output shaft, wherein the synchronizer is adapted to enable or interrupt a power transmitting between the transmission unit and the output unit; a differential cooperating with the output unit for power transmitting, wherein a driving gear of a main reducer is configured to externally mesh with a driven gear of the main reducer, and the driven gear of the main reducer is fixed on the differential, so as to transfer the power to the differential, and the differential distributes power and adaptively transfers the distributed power to half axles at two sides of the vehicle, to drive the front wheels; two third motor generators configured to drive the two rear wheels respectively. an engine unit configured to generate power; a dual clutch, wherein the engine unit is coupled with an input terminal of the dual clutch; a transmission unit adapted to selectively couple with the engine unit, and configured to transmit the power generated by the engine unit, the transmission unit comprising a first input shaft and a second input shaft, wherein the second input shaft is coaxially fitted over the first input shaft, the first input shaft is coupled with a first output terminal of the dual clutch, and the second input shaft is coupled with a second output terminal of the dual clutch, each of the first input shaft and the second input shaft is provided with one fixed driving gear; an output unit configured to transmit the power output by the transmission unit; a first motor generator coupled with the one driving gear on the second input shaft via an intermediate gear (411, 44, 451, 452), wherein the engine unit and the first motor generator are configured to drive the front wheels; an output shaft, provided with two driven gears, wherein the two driven gears are configured to mesh with the driving gears on the first input shaft and the second input shaft, to form two gears; a synchronizer, disposed on the output shaft, wherein the synchronizer is adapted to enable or interrupt a power transmitting between the transmission unit and the output unit; a differential cooperating with the output unit for power transmitting, wherein a driving gear of a main reducer is configured to externally mesh with a driven gear of the main reducer, and the driven gear of the main reducer is fixed on the differential, so as to transfer the power to the differential, and the differential distributes power and adaptively transfers the distributed power to half axles at two sides of the vehicle, to drive the front wheels; two third motor generators configured to drive the two rear wheels respectively.