A novel microstrip switchable diplexer for 5G communication systems is proposed in this paper, which is composed of three terminated T-shaped resonator (TTSR) with only two pin diodes as the switch elements. The desired passband can be achieved by a common TTSR work together with two loaded TTSRs, and the independently switchable channels are formed by the different on/off states of the pin diodes. In particular, two transmission zeros are generated by the TTSRs in the stopband to sharp the passband edges and improve the isolation between the two passbands. Simulations and measurements are carried out to verify the design concept with good agreement.