Hydrodynamicmechanical transmission system and hydrostaticmechanical transmission system are two important transmission system layout schemes of underground load haul dump(LHD) unit. For the transmission system design of ACY10 small underground LHD which load was 1 m3, according to the use requirements, the variable pump and motor components were designed. The hydrostaticmechanical transmission scheme was chosen. Different vehicle hydraulic system analysis models were built based on Automation studio, and the operating characteristics of driving hydraulic system, steering hydraulic system and working hydraulic system were analyzed. When the system was operated under different conditions, the system oil circulation, the dynamic load characteristic of the system, and the pressure and the position curves of the working cylinder changing with time were gotten. Similarly, according to the characteristics of the hydrodynamicmechanical transmission system, the analysis model was built. The characteristics of the hydrodynamicmechanical transmission system and the hydrostaticmechanical transmission system were comparative analyzed. The results show that the hydrostaticmechanical transmission scheme has advantage in the maximum traction force, maximum digging force and climbing ability, and the tilting fluctuation phenomenon appeared in the cylinder system is solved well.So the stability of the hydraulic system is improved. The hydrostaticmechanical transmission scheme can be taken as a design reference.