Abstract: This paper presents a design scheme of three-pass band filter based on the branch loaded resonator. The cutoff frequency of the resonator is related to the electrical length and characteristic admittance of the open branch. LTCC process and grounding capacitance structure are used to reduce the size of the filter,and the branch symmetry structure is used to reduce the complexity of the design. After theoretical calculation and 3 d electromagnetic field simulation optimization,the size of the band-pass filter is 4.8 mm × 4.2 mm × 1.5 mm. With processing test and comparison,the in-band echo loss is less than 10 dB,and the out-of-band suppression is more than 15 dB. Therefore,it can conclude that this design scheme can meet the actual requirements and can be used for the RF front-end with requirements for multi-band communication.