The hydraulic drive system is one of the transmission systems of construction machinery,and the multifunction hydraulic test bench is a scientific experiment platform for construction machinery hydraulic transmission system study.The element selection of closed motor pump system of a kind of multifunction hydraulic test bench was introduced.According to the experimental requirements,a closed motor met test purposes was chosen;according to the motor parameters,the parameters of the closed pump and motor matched with the motor were calculated.Adopting the selected components,the closed motor pump system was designed;then the modeling and simulation were carried using AMESim.The curves of the motor speed,torque,pump outlet pressure were gotten.The simulation results verify the validity and rationality of the designed hydraulic system,and the correctness of the component selection.