A dual-band independently tunable bandpass frequency selective surface loaded with varactor diodes is designed, in which the unit structure consists of a composite metal surface loaded with varactor diodes, a Rogers RT5880 dielectric layer and an underlying cross feeder. Based on the finite difference time domain method and the equivalent circuit method, the structure of the designed model is optimized, and its electromagnetic characteristics are verified. The results show that when the equivalent capacitance of 0.2, 0.4, 0.6 pF and 0.03, 0.06, 0.08 pF is loaded at the outer ring and the inner ring respectively, the resonant center frequency drifts to the low frequency with the increase of the capacitance, and the low frequency passband and the high frequency passband can be modulated respectively. Based on the surface electric field distribution at the resonant frequency, the physical mechanism of dual-band frequency tunability is expounded in detail. The designed dual-band independently tunable bandpass frequency selective surface model has a simple bias network structure without considering additional feeders, which provides a new idea for active reconfigurable devices in the microwave band.