The invention discloses a terahertz subharmonic frequency doubling and mixing device based on a monolithic integrated circuit. The device comprises a fundamental wave input waveguide micro-strip transition, a CMRC structure local oscillator low-pass filter, a frequency doubling matching circuit, a four-die frequency doubling diode, a local oscillator matching circuit, a frequency mixing diode, a radio frequency matching circuit, a radio frequency input waveguide micro-strip transition, and a CMRC structure intermediate frequency low-pass filter. According to the terahertz subharmonic frequency doubling and mixing device based on the monolithic integrated circuit, on the one hand, the number of dielectric substrates is decreased, and circuits are integrated on one substrate, so that the number of cavities to be processed is decreased, and processing and assembling are easy; on the other hand, waveguide transitions to be designed and processed are reduced, and the cavity size is reduced.