A frequency hopping bandpass microwave photonic filter based on Lyot-sagnac filter and cascaded structure was proposed. In the filtering system, a continuous optical source with variable wavelength separation is achieved by using broadband source and Loyt-sagnac filter. The first order filter is composed of a phase modulator and a signal mode fiber. A ring resonator is cascaded to be the second order filtering structure. A frequency hopping single-bandpass microwave photonic filter with high Q-factor is achieved by cascading the two filters. In the case of choosing three sections of polarization maintaining fiber, the central frequency of the filter is hopped among 1.012 1 GHz, 1.214 5 GHz, 1.416 9 GHz, 1.619 3 GHz and 1.821 7 GHz by adjusting the polarization state of polarization controller. Since a cascaded structure is used in this article, the implementation of the filter inherited advantage of both filters. So the filter has good frequency response. The highest Q-factor is 13 155.69. Main side lobe suppression radio varies from 18 dB to 25.51 dB. Besides, the device has simple structure and is easy to control.