With the development of 5G communication technology, RF frontend devices tend to be integrated and miniaturized, making the film bulk acoustic resonator (FBAR) technology one of the research hotspots in the field of communication. In this article, the trapezoidal cascade method is selected for different order number of FBAR resonant unit, and the MBVD equivalent circuit model is established by using the RF simulation software ADS. The performance parameter output curve of FBAR is simulated by experiment, and a high frequency narrowband filter within the 5G frequency band (4.8~5.0 GHz) standard planned by the Ministry of Industry and Information Technology is designed. The experimental results show that the designed FBAR frequency band is at the range of 4.849~4.987 GHz. It is found that the increase of cascade order of FBAR unit can significantly improve the outofband rejection and the insertion loss is low, which satisfies the performance parameters requirements of the 5G communication system for the filter.