Under the action of waves, the ocean buoy device mainly undergoes pitch and heave motions. In this paper, a novel buoy wave energy harvester with multi-source coupling is proposed. The harvester employs a two-degree-of-freedom differential gear train to capture the pitch and heave motions of the buoy, with the output shaft of the differential gear train connected to the rotor of the generator. The power generation device utilizes a pendulum ball rotating around a fixed axis to capture the energy of the buoy′s longitudinal pitch motion, and a gear mechanism with unidirectional bearings is used to convert the reciprocating swing motion of the pendulum ball into unidirectional rotational motion to drive the generator, which serves as one input to the differential gear train. Simultaneously, the heaving motion of the buoy is converted into unidirectional rotational motion to drive the generator rotation through a gear rack mechanism with unidirectional bearings, acting as the other input of the differential gear train. The planetary carrier of the differential gear train serves as the output and is directly connected to the generator rotor, driving the generator to rotate in one direction. Ultimately, the kinetic energy of the buoy′s pitching and heaving motions is transformed into electrical energy. The dynamic equations of the pendulum ball generator, the float body generator, and the coupled pitch-heave motion in the buoy power generation device are established separately. Numerical simulations are conducted to study the dynamic response and power generation of the device under different wave periods and amplitudes. The results show that when the wave amplitude is 1 m, the average power generation of the buoy reaches its maximum at a wave period of 2. 3 s. As the excitation wave amplitude increases, the vibration responses of the buoy′ s pitching and heaving motions become more pronounced, and the power generation gradually increases. When the wave amplitude reaches 1. 1 m, the generated power can reach 525. 7 W. Additionally, when the wave period is 2. 3 s and the amplitude is 1 m, the installation of unidirectional bearings can increase the power generation efficiency by approximately 19. 2% compared to not installing unidirectional bearings.