A new type of five order tunable tapped comb line filter has been presented in this paper.The designed device uses the coplanar ground and uses the ferroelectric film Ba0.6Sr0.4TiO3(BST) parallel plate capacitors as the tunable component.The effect of the plate capacitor on the device has been analyzed.Aiming at the condition that a DC bias and high resistance for isolation are required for the comb line filter,a method which uses the high capacity BST capacitor integrated on the substrate as the isolation capacitor and interconnects the bias lines of each order resonator to simplify the pressure procedure has been proposed the first time in this work. The design is simulated and verified by software of HFSS.The designed filter has the center frequency tuning range of 842~960 MHz(14%) and 3 dB bandwidths of 9%~10%.