A control system for a hybrid vehicle in which an engine and a first motor are connected to an input side of an automatic transmission, and a second motor is connected to drive wheels (8, 10), comprising: a controller that controls the first motor and the second motor, wherein the controller is configured to calculate a required drive force, and execute a selective control to selectively execute a first assist control to raise an input speed to the automatic transmission by the first motor, and a second assist control to increase an output torque of the second motor thereby increasing a drive force to propel the hybrid vehicle, based on the required drive force; characterized in that the controller is further configured to execute an acceleration demand determination to determine whether a driver intends to accelerate the hybrid vehicle, execute a drive force determination whether the output torque possible to be generated by the second motor is insufficient to achieve the required drive force to accelerate the hybrid vehicle, after executing the acceleration demand determination, select the first assist control when the output torque possible to be generated by the second motor is insufficient to achieve the required drive force, and select the second assist control when the second motor is allowed to generate the output torque to achieve the required drive force; and wherein the acceleration demand determination is made based on an increase in the required drive force and a satisfaction to execute a downshifting of the automatic transmission, and the first assist control is executed to expedite execution of the downshifting by raising the input speed by the first motor; wherein the controller is further configured to determine whether the downshifting to be executed in response to an increase in the acceleration demand is a step shifting to shift a gear stage of the automatic transmission to a target stage that is two or more stages lower than the current stage via an interim stage, execute the first assist control to expedite execution of the downshifting by raising the input speed to the automatic transmission by the first motor until the completion of the downshifting, if execution of the step shifting is determined, and execute the second assist control to drive the second motor when shifting the gear stage from the interim stage to the target stage. a controller that controls the first motor and the second motor, wherein the controller is configured to calculate a required drive force, and execute a selective control to selectively execute a first assist control to raise an input speed to the automatic transmission by the first motor, and a second assist control to increase an output torque of the second motor thereby increasing a drive force to propel the hybrid vehicle, based on the required drive force; characterized in that the controller is further configured to execute an acceleration demand determination to determine whether a driver intends to accelerate the hybrid vehicle, execute a drive force determination whether the output torque possible to be generated by the second motor is insufficient to achieve the required drive force to accelerate the hybrid vehicle, after executing the acceleration demand determination, select the first assist control when the output torque possible to be generated by the second motor is insufficient to achieve the required drive force, and select the second assist control when the second motor is allowed to generate the output torque to achieve the required drive force; and wherein the acceleration demand determination is made based on an increase in the required drive force and a satisfaction to execute a downshifting of the automatic transmission, and the first assist control is executed to expedite execution of the downshifting by raising the input speed by the first motor; wherein the controller is further configured to determine whether the downshifting to be executed in response to an increase in the acceleration demand is a step shifting to shift a gear stage of the automatic transmission to a target stage that is two or more stages lower than the current stage via an interim stage, execute the first assist control to expedite execution of the downshifting by raising the input speed to the automatic transmission by the first motor until the completion of the downshifting, if execution of the step shifting is determined, and execute the second assist control to drive the second motor when shifting the gear stage from the interim stage to the target stage.