A power transmission system for a vehicle, comprising: an engine; a plurality of input shafts (11, 12), wherein at least one of the input shafts is configured to engage with the engine; each of the input shafts having a shift driving gear thereon; a plurality of output shafts (21, 22), wherein each of the output shafts has a shift driven gear configured to mesh with a corresponding shift driving gear; a generator gear fixed on one of the output shafts; a reverse output gear configured to rotate together with or to disengage from a shift driving gear; an output idler gear, wherein the output idler gear is configured to engage with one of the output shafts so as to rotate together with the output shaft or to disengage from one of the output shafts so as to rotate with the output shaft at a different speed; a motor power shaft, wherein the motor power shaft is configured to rotate together with the generator gear; and a first motor generator configured to rotate together with the motor power shaft; further comprising an output idler gear synchronizer configured to synchronize the output idler gear with one of the output shafts (21, 22); further comprising a motor power shaft gear fixed on the motor power shaft and configured to mesh with the generator gear; characterized by further comprising a reverse idler gear (711, 712, 713) configured to rotate together with a shift driving gear; wherein the reverse output gear is configured to selectively rotate together with the reverse idler gear; further comprising a reverse synchronizer configured to synchronize the reverse output gear with the reverse idler gear, wherein the reverse synchronizer and the output idler gear synchronizer are configured to share a shift fork mechanism; wherein the output idler gear synchronizer is configured to be in a disengaged state when the reverse synchronizer synchronizes the reverse output gear with the reverse idler gear; and wherein the reverse synchronizer is configured to be in a disengaged state when the output idler gear synchronizer synchronizes the output idler gear with one of the output shafts (21, 22). an engine; a plurality of input shafts (11, 12), wherein at least one of the input shafts is configured to engage with the engine; each of the input shafts having a shift driving gear thereon; a plurality of output shafts (21, 22), wherein each of the output shafts has a shift driven gear configured to mesh with a corresponding shift driving gear; a generator gear fixed on one of the output shafts; a reverse output gear configured to rotate together with or to disengage from a shift driving gear; an output idler gear, wherein the output idler gear is configured to engage with one of the output shafts so as to rotate together with the output shaft or to disengage from one of the output shafts so as to rotate with the output shaft at a different speed; a motor power shaft, wherein the motor power shaft is configured to rotate together with the generator gear; and a first motor generator configured to rotate together with the motor power shaft; further comprising an output idler gear synchronizer configured to synchronize the output idler gear with one of the output shafts (21, 22); further comprising a motor power shaft gear fixed on the motor power shaft and configured to mesh with the generator gear; characterized by further comprising a reverse idler gear (711, 712, 713) configured to rotate together with a shift driving gear; wherein the reverse output gear is configured to selectively rotate together with the reverse idler gear; further comprising a reverse synchronizer configured to synchronize the reverse output gear with the reverse idler gear, wherein the reverse synchronizer and the output idler gear synchronizer are configured to share a shift fork mechanism; wherein the output idler gear synchronizer is configured to be in a disengaged state when the reverse synchronizer synchronizes the reverse output gear with the reverse idler gear; and wherein the reverse synchronizer is configured to be in a disengaged state when the output idler gear synchronizer synchronizes the output idler gear with one of the output shafts (21, 22).