A driving assembly to be longitudinally placed in a vehicle, having a single power source , connected to a transmission shaft or a vehicle axle half shaft of the vehicle, provided with an automatic transmission, characterized in that : the automatic transmission comprises an input shaft , a power source is connected to the input shaft , an output shaft is provided coaxial with the input shaft , and an intermediate shaft is provided parallel to the input shaft ; and a first-stage reduction-gear train is installed through the input shaft and the intermediate shaft , an Nth-stage reduction-gear train is installed through the intermediate shaft and the output shaft , N≥2, and each of the stages of the reduction-gear trains comprises a pair of gears having a different transmission ratio; characterized in that the output shaft of the power source and the input shaft of the automatic transmission are integrally manufactured, a rear cover of the power source and a front housing of the automatic transmission are integrated, and the driving assembly is placed in the front of the vehicle, and drives rear wheels of the vehicle; wherein longitudinally placed refers to that all of the axial direction of the output shaft of the power source and the axial directions of the input shaft , the intermediate shaft and the output shaft of the automatic transmission are in the direction of the length of the vehicle; wherein the first-stage reduction-gear train comprises an upper gear and a lower gear, the upper gear is fixedly connected to the input shaft of the automatic transmission via a key, the lower gear is fixedly connected to the intermediate shaft of the automatic transmission via a key, and a shifting clutch is provided between the upper gear and the input shaft of the automatic transmission; the shifting clutch is of an electromagnetically driving mode, and comprises a fixed fluted disc, a movable fluted disc and a power winding, the fixed fluted disc and the upper gear are integrated, the movable fluted disc is fixedly connected to the output shaft of the automatic transmission via a key, and when the power winding is electrified, the movable fluted disc moves axially along the output shaft of the automatic transmission to engage with the fixed fluted disc; the power winding is a sector-shaped winding, a semi-circular winding or a ring winding. the output shaft of the power source and the input shaft of the automatic transmission are integrally manufactured, a rear cover of the power source and a front housing of the automatic transmission are integrated, and the driving assembly is placed in the front of the vehicle, and drives rear wheels of the vehicle; wherein longitudinally placed refers to that all of the axial direction of the output shaft of the power source and the axial directions of the input shaft , the intermediate shaft and the output shaft of the automatic transmission are in the direction of the length of the vehicle; wherein the first-stage reduction-gear train comprises an upper gear and a lower gear, the upper gear is fixedly connected to the input shaft of the automatic transmission via a key, the lower gear is fixedly connected to the intermediate shaft of the automatic transmission via a key, and a shifting clutch is provided between the upper gear and the input shaft of the automatic transmission; the shifting clutch is of an electromagnetically driving mode, and comprises a fixed fluted disc, a movable fluted disc and a power winding, the fixed fluted disc and the upper gear are integrated, the movable fluted disc is fixedly connected to the output shaft of the automatic transmission via a key, and when the power winding is electrified, the movable fluted disc moves axially along the output shaft of the automatic transmission to engage with the fixed fluted disc; the power winding is a sector-shaped winding, a semi-circular winding or a ring winding. <EOS>