The invention provides an improved eight-gear transmission which mainly comprises an input shaft, an output shaft, planet gear rows, connecting components and torque transmission devices. The input shaft, the output shaft, the planet gear rows, the connecting components and the torque transmission devices are arranged in a transmission shell. Each planet gear row comprises a sun gear, a planet carrier, a planet wheel and a gear ring. Each torque transmission device comprises two clutches and four brakes, wherein the two clutches and the four brakes are connected selectively so that the sun wheels, the planet carriers, the gear rings and one of the five connecting components can rotate or can be fixed. In addition, at least two torque transmission devices can be connected selectively in a combined mode so that eight forward gear speed ratios and one reverse gear ratio can be established between the input shaft and the output component; the forward gears are five deceleration gears, one direct gear and two overspeed gears. The transmission is compact in structure, low in weight, small in size and easy to arrange on an automobile, and the speed ratio step among the gears of the transmission meets the requirement of the transmission.