The instantaneous discharge and the flow fluctuation of SCY 14B type axial piston pump were theoretically analyzed, and simulations of pumps with seven pistons and eight pistons were made using MATLAB. The simulation results show that: the flow fluctuation coefficient of piston pump with odd number is lower than that of piston pump with even number leaving out the influence of geometrical factors. The flow fluctuation varies inversely as the piston number. And the larger the swash plate angle is, the greater the discharge of the pump will be. But the angle of the swash plate has no effect on the flow fluctuation. The flow fluctuation coefficient of piston pump with odd number is almost no different than that of piston pump with even number, if the influence of geometrical factors and leakage are taken into consideration; but it is significantly larger than the theoretical flow fluctuation coefficient. And the geometric flow pulsation is the major aspect that affects the flow pulsation characteristics.