Abstract: In order to facilitate the design of articulated transport vehicles in coal mines, the design and development of gearboxes for hydro-mechanical transmission systems are needed. The key technologies of the design of number of gears and shift control of a certain fixed-shaft power shift transmission, the determination of the transmission ratio of each gear, the determination of the center distance between the input and output, the design of the shift and reverse clutch, combination mode of each gear clutch?and the design of the structure are described. Transmission bench test transmission efficiency ranges from 96.3% to 98.5%, and the maximum temperature of transmission oil is 88.5 ℃. The average maintenance cycle of gearbox loading is 8 months, and the full life cost is equivalent to imported parts, which can replace imported ones. By changing the transmission ratio of each gear，series design of fixed shaft power shift gearbox can be used for articulated transport vehicles with different loads，it can solve the problem that the key technology of trackless auxiliary transport vehicle relies on import for a long time.