A tunable terahertz tri-band bandstop filter based on reconfigurable metamaterials was designed.The filter consists of a movable part and a fixed part,and two parts are both Au-Si two layer structure.The thickness of gold is 0.65 μm,and that of the silicon layer is 25 μm.The movable part is drived by electrothermal driver and its maximum displacement is 5 μm.The movable part is a rectangular ring with different side lengths,and the fixed part is a split-ring-resonator(SRR).Finite integration time domain(FITD) method is applied to analyze the performance of filter.According to the distribution of surface currents,the equivalent circuit models are set up.The surface current distribution shows that the center frequency of the third stopband is generated by the dipole oscillation on the surface of movable part,and the center frequency of the first two stopbands are generated by low frequency dipole resonance and high frequency dipole resonance on the fixed part,respectively.The designed tunable bandstop filter has important application value in the field of terahertz communication and frequency-selective terahertz detection.