An easytouse 4step design method for FBAR filters was presented, and demonstrated by a design case of FBAR Rx filter for FDDLTE Band 7. According to the center frequency and bandwidth of FBAR filter, the thicknesses of each film in the FBAR film stack layer were determined at the step 1. The step 2 gets the filter′s circuit architecture. In the step 3, we obtain the active area of each FBAR unit. To get this, the active area of series FBAR units and the ratio of active area of parallel FBAR units and series FBAR units were used as two groups of optimization parameters reasonably. Taking the given insertion loss and outofband rejection of filter as the optimization objectives,we obtained the optimized values by the algorithm based on gradient in ADS software. The step 4 aimed at minimizing the filter passband ripple. In the design case, this aim was fulfilled by a novel FBARs′ electrode layer thickness adjusting method, and intentionally slightly mismatched the series resonant frequency of the series FBAR units with the parallel resonant frequency of the parallel FBAR units. As in the design case results, a SiO2 support layer with only 300 nm needed to survive the backside viahole etching microfabrication process, a buried oxide layer (BOX) buffered 2step viahole etching scheme was proposed in this work, which taking advantage of the etching selfstop characteristic of BOX. The study results showed that the insertion loss of the Rx filter was 0.6 dB, outofband rejection in Tx frequency band was 40.4 dB and the passband ripple was 0.4 dB. The feasibility of the design method was validated from this.