Abstract: A novel technique was developed for dimension measurement of assembled traveling wave tube(TWT)with imported coordinate measuring machine(CMM).The measurement comprises the input/output device distance,separation and parallelism between bottom of TWT assembling plate and output wave-guide,and coordinates of alignment points.The original work included the design of threaded transfer mold,optimization of measurement procedures,compilation of automatic measurement program,determination of reasonable forward/backward motion distances,and automatic generation of machining drawing of wave-guide connectors based on measured data by means of 3 D graphics software.Moreover,the accumulated errors,originated from the fabrication and assembling of TWT,were effectively compensated.The test results show that the self-developed measurement technique works pretty well.For example,the orientation and position of final installation port on wave-guide connector satisfies the design requirements.