Abstract: In order to solve the cooling problem of a transceiver module with eight channels, a prototype of two-phase cooling system is designed based on the highly efficient thermosyphon loop in this paper. The start-up characteristics of the system and the influence of work inclination angle and condensing ability on its cooling performance are studied experimentally. The results show that the start-up characteristics and the work performance of the system are good with changes from -30°~75° of the work inclination angle, which ensures normal operation of the transceiver module. As the velocity of condensing air increases, the cooling capacity of the system is improved greatly with higher power consumption of fans. It also can be found that the comprehensive property of the cooling system is the best when the work inclination angle is 20° and the velocity of condensing air is 6.5 m/s. It has the cooling capacity for the transceiver module with power consumption of 475 W and local heat flux of 60 W/cm².