A transmission unit for a vehicle, comprising: a plurality of input shafts (11, 12), 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; the plurality of output shafts including a first output shaft and a second output shaft; a motor power shaft configured to rotate together with one of the output shafts; and an output unit configured to rotate with one of the output shafts at a different speed or configured to selectively engage with one of the output shafts so as to rotate together with the output shaft, wherein the motor power shaft is configured to rotate together with one of the output shafts via a gear pair, further comprising a motor power shaft gear fixed on the motor power shaft, and a generator gear fixed on the output shaft and configured to mesh with the motor power shaft gear, characterized by further comprising: a reverse output gear configured to selectively rotate together with a reverse idler gear; and a reverse idler gear configured to rotate together with a shift driving gear, further comprising a reverse synchronizer configured to selectively synchronize the reverse output gear with the reverse idler gear, wherein the reverse idler gears comprise: a first reverse idler gear configured to mesh with a shift driving gear; a second reverse idler gear configured to rotate together with the first reverse idler gear; a third reverse idler gear configured to mesh with the second reverse idler gear; and wherein the reverse synchronizer is configured to selectively synchronize the reverse output gear with the third reverse idler gear, wherein the reverse output gear is coaxially arranged with the third reverse idler gear; and wherein the reverse synchronizer is disposed on one of the reverse output gear and the third reverse idler gear and to engage with the other, wherein the reverse output gear and the third reverse idler gear are fitted over the motor power shaft, and the first reverse idler gear and the second reverse idler gear are both fitted over the second output shaft. a plurality of input shafts (11, 12), 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; the plurality of output shafts including a first output shaft and a second output shaft; a motor power shaft configured to rotate together with one of the output shafts; and an output unit configured to rotate with one of the output shafts at a different speed or configured to selectively engage with one of the output shafts so as to rotate together with the output shaft, wherein the motor power shaft is configured to rotate together with one of the output shafts via a gear pair, further comprising a motor power shaft gear fixed on the motor power shaft, and a generator gear fixed on the output shaft and configured to mesh with the motor power shaft gear, characterized by further comprising: a reverse output gear configured to selectively rotate together with a reverse idler gear; and a reverse idler gear configured to rotate together with a shift driving gear, further comprising a reverse synchronizer configured to selectively synchronize the reverse output gear with the reverse idler gear, wherein the reverse idler gears comprise: a first reverse idler gear configured to mesh with a shift driving gear; a second reverse idler gear configured to rotate together with the first reverse idler gear; a third reverse idler gear configured to mesh with the second reverse idler gear; and wherein the reverse synchronizer is configured to selectively synchronize the reverse output gear with the third reverse idler gear, wherein the reverse output gear is coaxially arranged with the third reverse idler gear; and wherein the reverse synchronizer is disposed on one of the reverse output gear and the third reverse idler gear and to engage with the other, wherein the reverse output gear and the third reverse idler gear are fitted over the motor power shaft, and the first reverse idler gear and the second reverse idler gear are both fitted over the second output shaft.