It is of great significance to carry out subglacial bedrock core drilling in polar regions for studying subglacial geology， revealing the evolutionary history of ice sheets and evaluating future climate change. The temperature of the drilling fluid may rise above 0°C after circulating at the bottom of the hole When drilling subglacial bedrock in polar regions， which may cause the wall of the icy hole to be melted during upward return， resulting in the instability of the wall， and even triggering the stuck drilling accident. It is necessary to design a drilling fluid cooling system that cooling the drilling fluid to a lower temperature before injecting it into the borehole， thereby keeping the drilling fluid below 0℃ at all times during circulation. The heat exchanger is the core component of the drilling fluid cooling system. The paper selects plate heat exchanger as the heat exchange component to cool drilling fluid， and uses the average temperature difference method to determine the heat exchange area and basic parameters， then numerical simulation of the heat exchange performance of the plate heat exchanger is using COMSOL Multiphysics 6.0 software. The research results show that the heat exchanger can cool the drilling fluid to -4~-3℃. Further， the simulation results show that the outlet temperature of the drilling fluid decreases with the decrease of the carrier refrigerant injection temperature and the increase of the carrier refrigerant flow rate， the type of drilling fluid has a great influence on the heat transfer performance of the heat exchanger， while the material of the heat exchanger plate has little influence.