Drive system for vehicle and controlling method thereof

A drive system (100) for a vehicle includes a driving source (2), a motor generator (6), a transmission (50), a clutch (3), and a control device (1) controlling the transmission (50) to receive a rotational torque of the output shaft (42, 43) transmitted from the driving wheel (Wr, Wl) at the motor generator (6) when a coast shift down is performed in a first state where the driving source (2) and the transmission (50) are disconnected from each other by the clutch (3) and the motor generator (6) is connected to the output shaft (42, 43) to receive the rotational torque, the control device (1) controlling the transmission (50) to receive the rotational torque at the driving source (2) by an engagement of the clutch (3) in a second state where the motor generator (6) is disconnected from the output shaft (42, 43) and does not receive the rotational torque.