The invention relates to a method for controlling the coupling and the decoupling of the first motor and of the second motor of a parallel hybrid motive power group comprising a first motor (11) driving an input shaft (4) at the entrance of a gear box (15), a second motor (12) and a coupling/decoupling means (13) of the second motor and of the first motor, maneuverable between an open position and a closed position, for enabling a change with regard to the gearbox when the motor group operates in hybrid mode, according to which the motive power group is controlled for decoupling the second motor and the first motor then changing the ratio of the gear box, and recoupling the second motor and the first motor. The laws of control of the motor group are used in such a manner that during the coupling and the decoupling, the torque set value for the input shaft comprises a discontinuity selected for compensating for the difference between the inertia produced by the input shaft when the second motor is coupled to the first motor and the inertia driven by the first input shaft when the second motor is decoupled from the first motor in order to avoid any sudden variation in acceleration of the input shaft driven by the motor group at the moment of decoupling or coupling.