Abstract: In order to suppress the switching frequency and its multiple harmonics effectively, a trap-inductor-capacitor- inductor (TLCL) filter topology is proposed. This filter topology can reduce the total inductance and maximum total energy storage of the filter and improve the dynamic response of the system under the harmonic attenuation requirements. Considering the skin effect of inductance at high frequency, the equivalent AC resistance is greater than DC resistance at high frequency. The decoupling analysis of the circuit is carried out, and a parameter calculation method to minimize the loss of parallel resonant branch (L_fn-C_fn) is derived. Reducing the total storage energy of the filter is an effective method to reduce the volume of the inductor and capacitor. By analyzing the increase of the storage energy in the resonant inductor and capacitor at the notch frequency and the decrease of the storage energy in the inductor and capacitor of other branches, it is proved that the TLCL filter can reduce the maximum total storage energy, thus reducing the size of the filter. Finally, taking buck converter as an example, the operation characteristics of buck converter based on TLCL filter and traditional LC buck converter are analyzed. The rationality of the theoretical analysis and the parameter design of TLCL filter is verified by simulations and experiments.