Abstract: A wind tunnel of high temperature and long operation time requires the use of cooling techniques,so we need design cooling channels on the nozzle. In this paper,rectangular cooling channels of high cooling efficiency were used to study the factors affecting nozzle cooling. First of all,a three-dimensional model of nozzle cooling structure was established. Secondly,the type of heat transfer of the nozzle was detailedly analyzed and at the same time radiation heat transfer was taken into account. Then based on the principle of simplicity and accuracy,a series of assumptions were made for the calculation model. Finally CFD techniques were used to carry out the numerical simulation. By analyzing the results of study,we obtained the rules how the aspect ratio of cooling channels influenced nozzle cooling,the difference whether or not considering radiation heat transfer,and the impact of gas flow total temperature on nozzle cooling.