Abstract: The basic principles of liquid cooling equipment and three basic forms of heat transfer are introduced. The thermal analysis procedure using professional thermal simulation software 6sigmaET is discussed indetail for a certain type of liquid cooling equipment. Based on the simulation result, the optimization of improving the flow-path performance and increasing the flow rate is proposed. Calculation indicates that the optimization can effectively improve the heat dissipation of the equipment. In this paper, the thermal design based on 6SigmaET improves the design efficiency and quality effectively, and provides reference value for the thermal design of similar liquid cooling equipment.