With the optimization goal of improving the transmission efficiency of the magnetically coupled resonant wireless power transmission (MCR-WPT) system, the influencing factors and suppression methods of frequency splitting phenomenon (FSP) are analyzed from the perspective of input impedance based on the mutual inductance model. Then we propose the Monte Carlo-Interior Point method (MC-IPM) for nonlinear modeling to determine the optimal system parameters while ensuring that the system does not suffer from FSP. Finally, the simulation results show that the proposed method can obtain the optimal parameters faster and achieve higher transmission efficiency. The optimized system can meet the practical requirements and provides a reference value for improving the transmission performance of MCR-WPT.