Abstract: A liquid cooling prototype developed for the 5G router with high heat flux density is introduced in this paper. The design of the key components of the liquid cooling system is shown. At the same time, simulation evaluation and regression analysis of the designed liquid cooling system are carried out. The test results show that under the designed flow rate, the chip heat dissipation requirements are reached, the system flow resistances match well and the deviation between the simulation results and the measured data is not more than 10%. At last, the benefit of the router liquid cooling system is evaluated from the perspective of power usage effectiveness (PUE). The results show that the PUE of the equipment room is less than 1.25. If the pure liquid cooling solution is adopted, the PUE will be reduced to 1.15. The application in transport network and server products will benefit more from the large-scale use.