Abstract: A novel dual composite right/lefthanded transmission line (D-CRLH-TL) is revised designed in this paper by applying the symmetrical spiralinterdigital figures to the traditional structure of DCRLHTL. Its electromagnetic characteristics are analyzed by the full wave simulator, and the simulated results show that this novel D-CRLH-TL has a good stopband with two controlled transmission zeros, compared with the traditional structure, it realizes a 30% size reduction. Then, a dualband bandstop filter with good performance is designed, fabricated and measured based on this novel D-CRLH-TL, the measured results show that the two stopband centered at 3.47GHz and 5.21GHz, and the bandwidth is 26.8% and 10% respectively, this filter can avoid the interferences come from the signals of WLAN and WMAX effectively. Moreover, compared with the traditional bandstop filter, the whole size of this designed bandstop filter is 20.9mm×12.6mm (0.24λ×0.15λ), and a 50% size reduction is realized.