In order to make the global coupling characteristic researches of axial piston pump possible, this paper analyzed the configuration and the coupling situation between the subsystems, and then a bond graph modeling method based on array was proposed to develop the dynamical model of piston pump. The energy loss factor was defined which contains swash plate angle, contact length between the piston and the cylinder, piston pair and slipper pair friction coefficient. So the state space model of piston pump was obtained by the tribology and dynamics coupling mechanism analysis of pistonslipper subsystem. The dynamical equation parameters of the subsystem which contains nonlinear factors are integrated in the global coupling dynamical model of piston pump clearly and concisely. The simulation results show that the coupling between the ripple of flow and pressure and the fluctuation of speed and torque becomes more obvious under high pressure, and the fluctuation of speed will influence the ripple of flow and pressure seriously when its amplitude reaches a certain level. The simulation results of piston pump running state and efficiency variation are in agreement with the actual situation. So the global coupling dynamical model of piston pump is effective and correct. Compared with the traditional local model of piston pump based on the assumption of constant pressure or constant speed, the global coupling dynamical model of piston pump established in this paper can be used to investigate energy saving and noise reduction, fault diagnosis, volume control and nonlinear dynamics analysis realistically.