Abstract: High fidelity transponder in space communication system requires higher linearity of high power TWT amplifier. Based on pre-distortion and feedforward linearization technology, a K band 50 W adaptive feedforward linearized TWT amplifier is designed for high frequency and high power applications. Its basic principle and parameters are introduced, and the parallel variable step-size combined adaptive algorithm is proposed. The distortion signal is adaptive cancelled under the condition of 20 dB of dynamic input power adjustment within 400 MHz bandwidth of K band. The third-order intermodulation is less than -35 dBc at the saturation output power back off 3 dB, which verified the great advantages of feedforward linearization technology in improving linearity.