The utility model belongs to double dynamical speed change gear of car. Its motor shaft inserts in the spline housing of bi -directional electric automatic clutch initiative dish, bi -directional electric automatic clutch is one epaxial at speed change gear by the internal spline of driving disk cover cartridge, the smooth dress of lower gear driving tooth and higher gear driving tooth is one epaxial at speed change gear, the higher gear passive gears, be connected with lower gear passive gears speed change gear power output shaft. The one way automatic clutch is overlapped the cartridge on the speed change gear input shaft by the driving disk internal spline, the stopping initiative is coiled with the spline cartridge on speed change gear power output shaft to with the stopping by the driving disk separation and reunion. The stopping axle can withstand the stopping piece of stopping on by the driving disk, and the stopping axle can inside and outside pulling on the transmission box. The utility model discloses can ensure the engine and the electromotor power and export effectively, and reverse next power can not be inputed to engine and motor, when motor and engine power stopped to export, the two clutch can autosegregation, and vehicle coast in traveling is reduce the running resistance and energy -conserving.