A low loss and high rejection duplexer based on the low temperature cofired ceramic (LTCC) technology is designed in this paper. The duplexer is composed of lowpass and highpass filters with LC structure, and a series resonance and a parallel resonance are respectively introduced into the two frequency bands of the duplexer to generate the transmission zero point, thereby the suppression effect and isolation of the duplexer is improved. The designed duplexer has the characteristics of low insertion loss, high isolation, high stopband rejection and small size. The experimental results show that the insertion losses of the duplexer both at the low frequency end from 095 GHz to 1.35 GHz and at the high frequency end from 1.65 GHz to 2.15 GHz are less than 2.5 dB, and the suppression at 1.65 GHz to 2.15 GHz and 0.95 GHz to 1.35 GHz is greater than 23 dB. It has a good application prospect.