Abstract: To reduce the system development risk of geosynchronous orbit synthetic aperture radar (SAR) satellite antenna with ten-kilowatt-level radiation power, a pulsed solid-state power amplifier(SSPA) is used to achieve a single channel output greater than 800 W, and then the transmission channel wired synthesis and spatial synthesis are used to meet the total pulse radiation power requirement greater than 18 000 W. The pulse SSPA is a critical payload of the system, which not only needs to provide pulse power, but also needs to consider power tolerance and long life requirements. The L-band spaceborne 800 W SSPA adopts a multipactor suppression design and bidirectional converter pulse load power compensation technology. Under the condition of 11.5% duty cycle, the power added efficiency including the power consumption is at least 50.3%, and the bus current ripple is less than 0.5 A. The dimensions of the SSPA are 299 mm×187 mm×75 mm and its weight is 4.0 kg, and it has passed space environmental tests and 2 800 hours high-temperature accelerated life test. The 20 SSPAs have been operating on-orbit for more than two years. To the authors′ knowledge, with 20 units operating in orbit for over two years, this is the highest pulse output power and power added efficiency among all verified spaceborne L-band SSPAs.