The invention belongs to the technical field of communication, and provides a bandwidth tunable microstrip filter to overcome the deficiencies of non-tunable performance and the like of the traditional microstrip filter. According to the bandwidth tunable microstrip filter, a physical mechanism is deeply analyzed by adopting an odd-even mode analysis method, and the influence of key parameters onthe performance of the tunable filter is revealed. The final simulation results and test results show that the bandwidth of the tunable filter can be adjusted in a wide frequency range; two sides of apassband are each provided with a transmission zero point, and the frequency selectivity can be effectively improved; and the bandwidth tunable microstrip filter has the advantages of high performance, small size, easy design and the like.