In the design process of magnetically coupled resonant wireless power transfer systems, different parameter selections significantly affect the system's output power and transmission efficiency, making it challenging to balance the two. This paper proposes an Improved Modified Sparrow Search Algorithm (IMOSSA) for optimizing system parameters. First, a mathematical model of the LCC-S circuit topology is constructed, and an in-depth analysis of the key parameters related to system output power and transmission efficiency is conducted. Based on this, an objective function is established with output power and transmission efficiency as the optimization goals, and working frequency, load resistance, and transmission distance as the optimization parameters. To enhance the algorithm's performance, three improvement strategies are proposed to refine the traditional Sparrow Search Algorithm (MOSSA), and optimization of the objective function is carried out accordingly. The simulation results demonstrate that, when compared to the MOSSA and NGSA-II algorithms, the solution set obtained by the IMOSSA algorithm demonstrates significant advantages in evaluation metrics. Under the specified weight coefficients, the IMOSSA algorithm achieves higher output power and transmission efficiency. Finally, the optimized parameters are validated through Maxwell simulation models, confirming their feasibility.