Natural gas hydrates are easily decomposed in the process of drilling cores because of an increase in temperature, so it is necessary to control the temperature of drilling mud in the mud refrigeration system below 0 ℃ to inhibit the decomposition of hydrate. Heat exchanger is the core equipment of the mud refrigeration system, and selecting a suitable heat exchanger structure is the key to obtain low temperature mud. The three key parameters of the minimum mud outlet temperature, temperature difference between the inlet and outlet and heat transfer power were taken as indicators to evaluate the effect of the three heat exchangers. The results showed that the minimum mud outlet temperature of spiral baffle heat exchanger could be ?2.1 ℃, and the inlet and outlet temperature difference reached 4.1 ℃, which showed a satisfied heat transfer result. Finally, the key process parameters of heat exchanger and the selection of key equipment of mud refrigeration system were proposed.