Ba0.6Sr0.4TiO3（BST）ferroelectric film was applied in micro strip circuit. A half wavelength tunable band pass filter was designed quickly by HFSS dual mode method to extract the coupling coefficients. Considering the voltage isolation of DC signal bias in the circuit, a high resistance line connecting line and a grounding wire of 1/4 wavelength was designed between the resonators. The filter tuning was simplified with dc voltage processing at port. The band pass tunable filter was finally designed with the features of 7.8 GHz center frequency and 1 GHz bandwidth.