In order to solve the problems of high resonance frequency and low output power of traditional piezoelectric energy harvesters, a T-type magnetically coupled piezoelectric energy harvester was proposed. By introducing the magnetically coupled interaction between the two sides, the piezoelectric beam is induced to generate bending-torsional vibration, which increases the deformation of the piezoelectric beam, and further enhances the output voltage response of the harvester. Firstly, the working principle and structural design of the piezoelectric energy harvester were analyzed, and its vibration characteristics were simulated and analyzed, and finally, the experimental prototype was made for experimental testing, and the effectiveness of the piezoelectric energy harvester was verified by simulation analysis and experimental tests. The results show that the optimal load resistance maximizes the output power. The energy harvesting frequency can be controlled by adjusting the weight of the mass at the free end of the device, and the output power improves with the increase of excitation acceleration. Introducing magnetic coupling, the influence of the bending-torsional coupling vibration caused by magnetic coupling on the output performance of the harvester was analyzed through comparative experiments. When the excitation acceleration is 0.2g, Due to the bending-torsion complex vibration, the working frequency and maximum output power of the magnetic coupling device III are 5.5 Hz and 3.71 mW, respectively. Compared to the energy harvesting device I, without magnetically coupled, the output power is increased by about 47%. Therefore the T-type magnetically coupled piezoelectric energy harvester has a high output efficiency in the low-frequency environment.