In this paper, a novel miniaturized microstrip duplexer with attenuation pole is proposed. A three-pole microstrip CT(Cascade Trisection) two bandpass filters have each asymmetrically prescribed transmission zero are design and fabrication. This CT bandpass filter changes coupling structure, which not only shifts the location of attenuation poles but also improves skirt characteristics. The duplexer results of measurement with the cross coupling CT bandpass filters has been yielded better isolation and sharper skirt behavior than that with a conventional bandpass filter. The results of measurement are almost similar to those of simulation results.