Abstract: Microchannel gas cooler is an important component of transcritical carbon dioxid e refrigerating equipment,and of great significance to system performance. Howe ver,few investigations have been made on this new type of heat exchanger.A stea dy-state distributed-parameter model is established,in which distributed proper ties of both carbon dioxide and air are considered.Through comparing simulation re sults with experimental results from literatures of American Air Conditioning an d Refrigerating Center,the model is accepted with an error within 13%.Then this model is used for sensitivity analysis of gas cooler performance to its configu ration parameters,such as microchannel diameter,number of microchannels,numbe r of tubes,number of processes.According the simulation results,it is suggeste d that the microchannel diameter should be within 0.7 to 1mm,and there should be 2 to 4 processes.