Abstract: The radar, guidance and communication are being operated at higher frequency, along with the develop ment of microwave solid state power devices and MMIC, the high power millimeter wave solid state amplifier becomes main research direction at home and abroad. A solid state transmitter has 50W CW output power working in Ka band is introduced in the paper. It has compact and high efficiency novel microstrip patch and waveguide double mode space couple power com biners,the combined efficiency is over 89%. The circuits design of power amplifier modules, chip mounting and bonding are described detailed in the paper. The circuit performances become worse due to the neglect of inductive impedance caused by bonding wires at higher frequency, the effects and solutions are also analyzed in the paper. The thermal design, controlling, protecting of the transmitter are also given in this paper. Through manufacture, test, the performances of the transmitter fully met the performance requirements, and has been successfully used in the system. By using the power amplifier modules, a larger output power transmitter can be easily obtained.