Wireless power transfer (WPT) systems serve as a means of electric power transmission for implantable medical devices (IMDs), and the parameters of the receiving coil play a crucial role in determining the power transfer efficiency (PTE). Currently, there is a lack of comprehensive research on sub-centimeter-sized coils specifically designed for medical applications. To address this gap, a parameter prediction method based on back propagation neural networks (BPNNs) is proposed. This method utilizes electromagnetic field finite element simulation data to accurately predict the coil's self-inductance, mutual inductance, and coupling coefficients, demonstrating a certain level of generalization capability. Moreover, the power transfer efficiency prediction is provided for a typical series-parallel resonant circuit. The effectiveness of the proposed method is verified through simulation and experimental results.