A power transmission system for a vehicle includes: an engine; input shafts, each of the input shafts being provided with a shift driving gear thereon; output shafts, each of the output shafts being provided with 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 configured to engage with one of the output shafts so as to rotate together with the output shaft or disengage from the output shaft so as to rotate with the output shaft at different speeds; a motor power shaft configured to rotate together with the generator gear; and a first motor generator configured to rotate together with the motor power shaft. A vehicle including the power transmission system is also provided.