The conventional CRHL TL based on the microstrip slot and reverse open loop resonator has limits on its application because of the narrow bandwidth and large reflection loss in pass band.Aiming at abovementioned problems, the conventional microstrip slot is replaced by Minkowski fractal microstrip slot to expand the bandwidth.Loading stub on both sides of the microstrip can also increase the bandwidth and improve the outofside rejection of high frequency end.The impact of size parameters of structure on the transmission characteristics is analyzed in this paper.The dispersion curve is calculated according to parameter S.Then,the equivalent circuit model is proposed.Finally,the bandpass filter with ultrawideband is designed by the proposed method.The bandpass filter uses only one CRLH structural unit and the ultrawideband of 2.1~9 GHz (relative bandwidth 124.3%) has been obtained. The reflection loss is smaller than 0.8 dB.At the same time,the transmission suppression of filter is larger than 20 dB at the stopband range of 9.5~12 GHz.The results of measurement and simulation are basically consistent with the result of equivalent circuit,which verifies the validity of the design method.