A novel bandstop resonant cell based on spiral interdigital structure is designed and analyzed by using the full wave simulation software. The simulated results indicate that there are two narrow stopbands in the proposed resonant cell, and the positions of the two narrow stopbands can be controlled respectively by changing the physical dimensions of the cell. Then, a compact dual band bandstop filter with good electromagnetic performances is designed and fabricated by cascading two cells. The filter is measured by the vector network analyzer and the measured and simulated results are in good agreement. The centre frequency of the two stopbands are 3.30 GHz and 4.93 GHz respectively, and the corresponding stopband bandwidth are 3.23 3.37 GHz and 4.73 5.10 GHz respectively. The sharpness of the stopband edge is greater than 90 dB/GHz, so this proposed filter has excellent performances. Moreover, the size of this filter is 24 mm×5.2 mm, thus has obvious advantage of miniaturization in comparison with the conventional bandstop filter.