A variable microwave photonic filter with wide tuning range is presented and analyzed theoretically. It is based on the stimulated Brillouin scattering (SBS) and uses two modulators to generate pump signal. By adjusting the modulation frequency of the two modulators separately, a fourpassband filter with switchable passband interval and dualpassband filter can be realized, and the center frequency of filter can be continuously tuned within a wide tuning range. Meanwhile, the 3 dB bandwidth of the filter remains unchanged. The effects of different modulation signals on the passband and the center frequency of the filter are simulated analyzed, as well as the relationship among the bandwidth and the pump power and the length of SBS gain medium.