To approach a high-efficiency, chip-size and widely tunable room temperature semiconductor terahertz (THz) frequency beating optical pumping beam source, an optical-integrated design is adopted. Two multipled distribute feedback (DFB) semiconductor lasers and a multimode interference (MMI) coupler are monolithically integrated on InP based substrate for terahertz frequency beating optical pumping beam generation. The designed Bragg wavelength spacing of the two DFBs is 4.8 nm (0.6 THz). The Bragg wavelength of the two DFBs can be tuned by the injected current. Each of them can red-shift by 3.9 nm. The output THz beating optical beam of the opticalintegrated chip can be coupled into the frequency resolved optical gate (FROG) through single mode fiber. By changing the injected current of the DFBs, room temperature THz frequency beating optical pumping beam source with a tunable frequency range of 0.184~1.02 THz is demonstrated.