A novel dual-channel monolithic circuit working at Q-band is reported which integrates the functions of Wilkinson power divider, digital attenuator and Single Pole Double Throw(SPDT) switch. Three-level parallel structure is adopted in the SPDT switch unit during the design process which can reduce insertion loss and improve isolation effectively. A kind of multi-section parallel-T structure is used in the digital attenuator unit for improving insertion loss and attenuation accuracy in high frequency band. By means of the above design，a monolithic circuit with 10 dB insertion loss and 26 dB isolation is produced successfully, which has the amplitude control function of 0.5 dB step to achieve 31.5 dB maximum attenuation.