In this paper, a design method of controller parameters is proposed for the controller of three-phase LLC resonant converter, which considers the influence of the peak of the amplitude-frequency characteristics of the converter on the stability of the system, and the controller parameters designed on this basis can realize the fast dynamic response speed of the system. In this paper, the small-signal model of three-phase LLC resonant converter is firstly established by using the extended descriptive function method to obtain its transfer function. By analyzing the frequency characteristics of the three-phase LLC resonant converter, a design method of controller parameters is proposed, and an experimental prototype is built to verify this method theoretically. The experimental results show that the controller parameters obtained by the design method of this paper can realize the fast dynamic response speed of the three-phase LLC resonant converter.