Concentrating on the high frequency demands of solid-state power amplifier （SSPA） for space usage， the methodology and key techniques of the Q band 20 watts， V band 10 watts and W band 2 watts SSPAs were proposed in the present study. The GaN HEMT monolithic microwave integrated circuits （MMICs） are utilized as basic power amplifier units for power and efficiency enhancement. The high efficiency multi-ways low loss power combination techniques including magic T and radial-line were developed to achieve high output power. Copper diamond and heat pipes were applied to overcome heat dissipation and thermal flux challenges. By considering the strictly space qualification and components derating requirements， all products show state-of-art performances， which are used and verified in application for satellites payloads or terminal transmitters. To the authors knowledge， this is the first time the EHF band SSPA are developed and qualified for space usage in China. The designs proposed in the paper meet the demands and requirements for future satellite projects， to strongly support high frequency and high throughput space communication tendency and targets realization.