Abstract: In this paper, a wide stopband filtering switch based on stepped impedence resonator (SIR) and stub line is designed. The state switching of the filtering switch is realized by regulating the PIN diode loaded on the feeding line. In the off-state, the PIN diode is on and the coupling structure between the feeding line and the resonator is designed with a coupling coefficient of zero, which effectively improves the isolation degree between the ports. In the open-state, when the PIN diode is disconnected, the stray frequency response is further removed from the fundamental frequency passband by adjusting the impedance ratio of the SIR, and the symmetrical stub lines are further loaded on the input and output feeding lines to suppress the first stray response, and the coupling structure between the resonators is used to suppress the second stray response, so as to achieve a wide stopband and avoid introducing additional loss into the circuit. The test results show that the isolation degree between ports is greater than 29 dB when the filtering switch is in the off-state. In the open-state, the passband center frequency f_A is 2.4 GHz, the in-band insertion loss is 1.2 dB, and the suppression effect is better than 20 dB in 3.2 GHz ~ 11.9 GHz (4.9 f_A), and the wide stopband suppression is realized.