A hybrid-power driving system, in which six forward speed ratios are available by switching only three synchronizers , comprising: an input shaft carrying a first driving gearwheel , a second driving gearwheel , a third driving gearwheel , and a fourth driving gearwheel disposed thereon; a first synchronizer , disposed on the input shaft , for releasably synchronizing at least one of the first driving gearwheel and the second driving gearwheel to the input shaft , a second synchronizer , disposed on the input shaft , for releasably synchronizing at least one of the third driving gearwheel and the fourth driving gearwheel to the input shaft ; an output shaft carrying a speed-reducing gearwheel , a first driven gearwheel , a second driven gearwheel , and a third driven gearwheel disposed thereon; a first intermediate shaft carrying a fourth driven gearwheel and a fifth driven gearwheel disposed thereon, wherein the first intermediate shaft includes a hollow portion and is coaxial to the output shaft ; a third synchronizer , disposed on the output shaft , for releasably synchronizing at least one of the first driven gearwheel and both the fourth driven gearwheel and the fifth driven gearwheel to the output shaft ; a second intermediate shaft carrying a sixth driven gearwheel , a seventh driven gearwheel , an eighth driven gearwheel , and a ninth driven gearwheel disposed thereon; a motor shaft carrying a fifth driving gearwheel disposed thereon; a final driven gearwheel ; a sixth driving gearwheel carried by the input shaft , wherein the ninth driven gearwheel is slidable to releasably mesh with the sixth driving gearwheel ; and wherein the sixth driving gearwheel is disposed on the second synchronizer . an input shaft carrying a first driving gearwheel , a second driving gearwheel , a third driving gearwheel , and a fourth driving gearwheel disposed thereon; a first synchronizer , disposed on the input shaft , for releasably synchronizing at least one of the first driving gearwheel and the second driving gearwheel to the input shaft , a second synchronizer , disposed on the input shaft , for releasably synchronizing at least one of the third driving gearwheel and the fourth driving gearwheel to the input shaft ; an output shaft carrying a speed-reducing gearwheel , a first driven gearwheel , a second driven gearwheel , and a third driven gearwheel disposed thereon; a first intermediate shaft carrying a fourth driven gearwheel and a fifth driven gearwheel disposed thereon, wherein the first intermediate shaft includes a hollow portion and is coaxial to the output shaft ; a third synchronizer , disposed on the output shaft , for releasably synchronizing at least one of the first driven gearwheel and both the fourth driven gearwheel and the fifth driven gearwheel to the output shaft ; a second intermediate shaft carrying a sixth driven gearwheel , a seventh driven gearwheel , an eighth driven gearwheel , and a ninth driven gearwheel disposed thereon; a motor shaft carrying a fifth driving gearwheel disposed thereon; a final driven gearwheel ; a sixth driving gearwheel carried by the input shaft , wherein the ninth driven gearwheel is slidable to releasably mesh with the sixth driving gearwheel ; and wherein the sixth driving gearwheel is disposed on the second synchronizer . <EOS>