Abstract: The traditional dual-band electrically tunable filter based on varactor has a bad insertion loss and a sharp decrease in fractional bandwidth due to the addition of external capacitance. Based on the multi-mode resonator, this paper proposes a novel dual-band band-pass tunable filter. The filter consists of a multi-mode resonator loaded with short-circuit branch line and a pair of quarter-wavelength resonators. At the end of each resonator, external bias circuit with varactor diode and quarter-wavelength resonator are loaded to consist the first passband, while short-circuit branch line loaded with resonator consists into the second passband, these two pass bands do not interfere with each other, they can be adjusted separately. By using the odd-even mode analysis and the method of adjusting the coupling length, two poles of each band will appear to ensure the stability of the bandwidth. The tunable range of the first passband is 0.7~0.85 GHz, the adjustable range of the second passband is 0.9~1.05 GHz. Meanwhile, the fractional bandwidth of the filter is kept above 10%. Compared with traditional dual-band filter, the proposed filter has an apparent increase of the fractional bandwidth.