Liquid metal is an attracting phase change material which has the advantages of high thermal conductivity，large volume latent heat and low volume expansion rate. It has potential application prospects in the field of aerospace thermal control. In order to explore the applicable scope of liquid metal phase change materials， the heat transfer performance and temperature control time between low melting point metal represented by gallium and paraffin phase change material represented by n-octadecane were compared and analyzed by numerical simulation. The results show that gallium module is more suitable to deal with transient high heat flux and short time operation of electronic electronic devices，while n-octadecane module is suitable for low heat flux and long-time operation of electronic devices.In addition，the thermal control time per unit volume of gallium module is longer than that of n-octadecane module； for unit mass of phase change material，the gallium module is dominant in a short time and n-octadecane module is dominant in a long time.The analysis of two space application scenarios shows that low melting point metal phase change materials can be used for antenna TR module and high power laser chip temperature control.