Abstract: This paper theoretically analyzes the dynamic behavior of the bistable piezoelectric energy harvester by high-frequency excitation and the bursting oscillation by low-frequency excitation, in order to find multiple high-energy orbits for the system, so as to improve the energy harvesting efficiency. First, the structure and general model of the bistable piezoelectric energy harvester are introduced. Different from the research in engineering, this paper mainly studies the motion, voltage output and efficiency of the energy harvester in terms of dynamics, including the in-well low-energy-periodic motion and the inter-well chaos motion by high-frequency excitation. It is shown that the bistable piezoelectric energy harvester will produce bursting oscillation in inter-well high-energy orbits by a single low-frequency excitation, but only has periodic motion in in-well low-energy orbits. At the same time, the existence and intensity of the bursting oscillation are investigated in combination with the amplitude and well depth. To explain the effects of high- energy and low-energy orbits on the energy harvesting efficiency, the variation of the output voltage for different values of equivalent damping and load resistance is discussed, and the optimal matching is derived. Finally, in the case of multiple low-frequency external excitations, different orbital combination modes are analyzed. It is found that the output voltage of double-high-energy bursting oscillation mode is the largest, followed by the combination mode of single-high-energy bursting oscillation and single-low-energy periodic oscillation, and the output voltage of double-low-energy periodic oscillation mode is the lowest. The comparison with single external excitation shows the good performance of multiple excitations.