The invention discloses a tunable microwave photonic filter based on a photoinjection semiconductor laser system. The tunable microwave photonic filter comprises a master laser, a first polarization controller, a variable optical attenuator, an optical circulator, a slave laser, a second polarization controller, a third polarization controller, a phase modulator, a fourth polarization controller, an opto-isolator, a 3dB optical coupler, a Sagnac loop filter, single mode dispersion fiber, an optical amplifier and a photoelectric detector. By making use of the nonlinear dynamic behavior of light when the light enters the semiconductor laser system, by exciting the single-cycle oscillation effect P1 of the semiconductor lasers to generate similar beam-shaped spectra with variable frequency space, and by adjusting the intensity of injecting the master laser to the slave laser or the off-resonance frequency between the two lasers, the invention realizes the tunable microwave photonic filter with a tunable filtering window and at the same time the reconfigurability and multi-tap structure of the filters are realized.