A power system for a hybrid vehicle, wherein the power system comprises an engine, a first electric motor, a second electric motor, a first planetary gear mechanism, a second planetary gear mechanism, a first input shaft, a first clutch, a second clutch, a first brake, a second brake, an intermediate shaft, and a differential; the engine is drivingly connected to the first electric motor, the first clutch is arranged between the first electric motor and the first input shaft, and the power transmission between the first electric motor and the first input shaft is cut off or combined by the first clutch; the second electric motor is arranged on the first input shaft for driving the first input shaft to rotate; the first planetary gear mechanism comprises a first sun gear, a first planetary gear, a first ring gear, and a first planetary frame; the first sun gear is fixed on the first input shaft to cause the first sun gear to rotate with the first input shaft; the second planetary gear mechanism comprises a second sun gear, a second planetary gear, a second ring gear, and a second planetary frame; the second sun gear and the first input shaft are independent of each other; the second ring gear is fixedly connected to the first planetary frame, the first ring gear is fixedly connected to the second planetary frame, the second ring gear is used to transmit the power output by the power system; the first brake is arranged between the second planetary frame and a casing of the power system; the second brake is arranged between the second sun gear and the casing of the power system, and the second clutch is arranged between the second sun gear and the first input shaft; the second ring gear is drivingly connected to the intermediate shaft through an output gear of the power system to transmit power to the differential through the intermediate shaft; the second electric motor is connected to the first input shaft through a third planetary gear mechanism, the third planetary gear mechanism comprises a third sun gear, at least one set of planetary gear, a third ring gear, and a third planetary frame; wherein one of the third sun gear, the third ring gear and the third planetary frame is fixed relative to the casing of the power system, a second rotor of the second electric motor is drivingly connected to one of the unfixed members to provide power thereto, and the other unfixed member is drivingly connected to the first input shaft in order to drive the first input shaft; wherein the power system further comprises an intermediate support plate fixedly installed on a front casing near one end of the second planetary gear mechanism, wherein a cavity is formed between the intermediate support plate and the front casing for installing the first brake, a third actuating cylinder for the first brake, the second brake, and a fourth actuating cylinder for the second brake. the engine is drivingly connected to the first electric motor, the first clutch is arranged between the first electric motor and the first input shaft, and the power transmission between the first electric motor and the first input shaft is cut off or combined by the first clutch; the second electric motor is arranged on the first input shaft for driving the first input shaft to rotate; the first planetary gear mechanism comprises a first sun gear, a first planetary gear, a first ring gear, and a first planetary frame; the first sun gear is fixed on the first input shaft to cause the first sun gear to rotate with the first input shaft; the second planetary gear mechanism comprises a second sun gear, a second planetary gear, a second ring gear, and a second planetary frame; the second sun gear and the first input shaft are independent of each other; the second ring gear is fixedly connected to the first planetary frame, the first ring gear is fixedly connected to the second planetary frame, the second ring gear is used to transmit the power output by the power system; the first brake is arranged between the second planetary frame and a casing of the power system; the second brake is arranged between the second sun gear and the casing of the power system, and the second clutch is arranged between the second sun gear and the first input shaft; the second ring gear is drivingly connected to the intermediate shaft through an output gear of the power system to transmit power to the differential through the intermediate shaft; the second electric motor is connected to the first input shaft through a third planetary gear mechanism, the third planetary gear mechanism comprises a third sun gear, at least one set of planetary gear, a third ring gear, and a third planetary frame; wherein one of the third sun gear, the third ring gear and the third planetary frame is fixed relative to the casing of the power system, a second rotor of the second electric motor is drivingly connected to one of the unfixed members to provide power thereto, and the other unfixed member is drivingly connected to the first input shaft in order to drive the first input shaft; wherein the power system further comprises an intermediate support plate fixedly installed on a front casing near one end of the second planetary gear mechanism, wherein a cavity is formed between the intermediate support plate and the front casing for installing the first brake, a third actuating cylinder for the first brake, the second brake, and a fourth actuating cylinder for the second brake.