Abstract: The waveguide subassemblies are the important parts of the radar. The welding quality of waveguide subassemblies affects greatly the performance and life-span of the radar. Compared with the traditional melting welding technology, the cold metal transfer (CMT) possesses an obvious advantage especially in waveguide subassemblies welding. With this technology the efficiency and quality of welding can be greatly improved while the welding strain can be sharply decreased. This paper introduces the characteristics of CMT and its application to waveguide subassemblies welding.