The invention discloses a minimal broadband electric tunable cavity filter which solves the problem that a conventional electric tunable filter can not realize tuning in broadband and the size is large. The structure includes five-stage cascade resonators, a square inner cavity is arranged in the open circuit end of each-stage of resonator, a rectangular notch is arranged on one side of the bottom, and an L-shaped branch is loaded on the open circuit end of the resonator to reduce size. One end of a tuning screw is screwed in the square inner cavity, and the other end passes through a dielectric substrate and electrically connected with the center of a metal sheet on the dielectric substrate. The metal sheet and a grounding metal ring are connected sequentially through four capacitor-pad-PIN switches, and each stage of resonator realizes group selected loading for the four capacitors to realize resonant frequency tuning. PIN switches in the same capacitor of the five resonators share a dc offset voltage source to control the on/off of the four voltage sources, thereby realizing rapid frequency modulation of the filter. Tuning in broadband is realized, and the size is small. Tuning in broadband is possible, the minimal broadband electric tunable cavity filter as a basic element of a microwave circuit is applicable to the front section of radio frequency of a wireless communication system.