Ambient environments are rich in rotational energy resources. These can be converted into useful electric energy through energy conversion materials to， powering embedded devices and wireless sensors in the Internet of Things. As such， energy har? vesting technology could potentially address the environmental pollution and high maintenance costs associated with traditional chemical batteries. This paper proposes a novel time-varying potential well magnetic-coupled bistable energy harvesting system with low potential barriers to enhance the energy harvesting performance in ultra-low frequency rotating environments （below 3 Hz）. The proposed system comprises a forward steel beam and an inverted piezoelectric beam installed on a rotational plate. Mutu? ally exclusive magnets are attached to the free ends of both beams， creating three equilibrium positions due to the magnetic force， two of which are stable. This gives the system its coupled bistable characteristics. The free end of the forward steel beam is dis? tanced from the center of the rotational plate， making it a centrifugal hardening beam. Conversely， the free end of the inverted piezoelectric beam is closer to the center， making it a centrifugal softening beam. Taking into account the influence of the centrifu? gal effect， the distributed parameter electromechanical coupling equation of the system is derived in the rotational coordinate sys? tem using the energy method， Lagrange equation， piezoelectric theory， and more. A magnetic calculation model is used to analyze the influence of magnetic spacing and the centrifugal effect on the potential energy well and the energy harvesting performance of the system. Finally， numerical simulations and experimental results verify that， compared to the linear energy harvesting system， the proposed magnetic-coupled bistable energy harvesting system has a wider operating frequency range （0~2.67 Hz） and higher output voltage （greater than 2 V）