The shipboard power system needs to provide safe and stable electrical energy for all kinds of electrical equipment. Therefore, a variety of power and electronic devices are used to complete the power conversion. These devices will inevitably bring various harmonic interference. In the high-power power system, due to the restrictions of the volume and weight, if we use EMI filter to filter out the rectifier DC side low-harmonics, due to the larger capacitance inductance, inductance need to bear all the working current, the aim is difficult to realize. In the case of known harmonic frequencies, in this paper, the principle of resonant filter can effectively reduce the volume of the filter in the case of ensuring the filtering effect, and an optimal design method of the resonant filter is proposed based on the genetic algorithm. Firstly, the basic principle and the design scheme of the resonant filter are expatiated. Then, the initial investment of the resonant filter, the harmonic content of the filtered DC side and the volume of the filtering device are taken as three targets, the genetic algorithm is used to optimize the parameters of the resonant filter. Finally, the experimental results show that the designed resonant filter has good comprehensive performance.