Abstract: The control technology of inner cavity brazing quality was studied for the millimeter wave guide antenna. A variety of analysis methods were carried out, such as electrical performance simulation, image processing analysis, ultrasonic C-scan detection analysis, metallographic analysis and so on. The influence of brazing parameters on the cavity quality was grasped. The results show that the imperfection defect was related to the position of the waveguide, and the brazing pressure and the thickness of the brazing filler metal are the important influencing factors on the cavity quality. When the brazing pressure was low, there is no solder overflow situation, but prone to no penetration defects. When the pressure was high, the waveguide around the permeability is 100%, but prone to solder overflow phenomenon. The thickness of the brazing material can be reduced, and the solder accumulation at the corner of the brazing and the penetration of the brazed seam can be effectively reduced. In order to obtain high-precision cavity-quality millimeter waveguide antenna, a higher pressure, thinner brazing filler metal are recommended to apply.