The main goal of this paper is studying characteristics of the parasitic motion principle (PMP) piezoelectric actuator and providing a dynamic model for possible control and optimization in future. Through analyzing motion principle of the PMP piezoelectric actuator and considering elastic deformation between the mover and the flexible mechanism, this paper first presents a dynamic model which is verified to be feasible through fitting experiment data. Then the model is used to analyze influence of the coupling angle, the driving signal symmetry, the mover mass and the preload force on performance of the PMP piezoelectric actuator, including the step length, the backlash ratio and the maximum output force. This research contributes to enhance the understanding of the PMP and provide a guidance for design of the PMP piezoelectric actuators.