A new method of bandpass filter design is proposed by using the CRLH transmission line theory. The method starts from the dispersion diagram of CRLH transmission line and is based on the negative first order and zero order resonance modes of an unbalanced CRLH transmission line. The relationship between the new method and conventional coupling method of filter design is discussed. By using the new method, a two-order mushroom filter is designed, fabricated and tested in this paper. The filter achieves a small size and a wide-stopband. Index Terms-Bandpass filter, Mushroom, Negative order resonator, Zeroth-order resonator, Wide stop-band.