Magnetic energy harvesting has higher power stability than solar and wind energy harvesting, and has greater output power compared to vibration energy harvesting. Therefore, it has become a research hotspot in the field of wireless charging for unmanned aerial vehicles (UAV) in recent years. The core structures of magnetic energy harvesting systems include closed-type and split-type. The split-type core structure shows broader application prospects due to the advantages of easy installation and disassembly. However, the split-core magnetic energy harvesting system still has shortcomings such as low modeling accuracy and suboptimal performance. Therefore, this paper establishes a harvested power prediction model for split-core MEH systems, which comprehensively considers the effective permeability of the core, the phase difference caused by magnetization current, and the power calculation under unsaturated states. Furthermore, a piecewise linear magnetization curve model is proposed, which outperforms the traditional linear model in terms of accuracy and has lower computational complexity than the arctangent model. Finally, an experimental magnetic energy harvesting system is built, and the experimental results show that the harvested power calculated using the proposed model is in good agreement with the experimental results.