The invention belongs to the field of radar electronic communication, and particularly relates to a transmitting device of a scene surveillance radar system. The transmitting device comprises a box-shaped housing and an upper cover board for closing the box opening of the housing. The box chamber of the housing forms an accommodating chamber for accommodating components. The components at least comprise a waveguide synthesizer, a coupler and a filter, wherein the waveguide synthesizer, the coupler and the filter are successively arranged in an engaging manner. The adjacent matching surfaces of the waveguide synthesizer, the coupler and the filter are flange surfaces and form a fixed flange fit. A shielding sealing ring which is used for improving electromagnetic shielding capability is embedded into each flange surface. The transmitting device has advantages of improving assembling and maintenance efficiency of the device, and effectively reducing or even preventing leakage of microwave signals. The transmitting device has advantages of high structure compactness, smaller device size, and effective improvement of convenience in maintenance.