To master the temperature distribution and "Solar cooker" of a Five-hundred-meter Aperture Spherical Radio Telescope(FAST) and to protect instruments in a feed cabin under the solar radiation, the temperature distributions of the FAST are studied in detail,which includes Sun parameters, "Solar cooker" calculation, heat flows and the temperature distribution of the FAST under different work conditions. The results indicate that the feed cabin temperature distribution is not only relevant to the reflector reflectivity, porosity rate, and the radiation time, but also to the reflectivity of the shield, materials, the diameter of microwave inlet and other factors. The analysis results of work conditions show that the reflector reflectivity is 0.2, porosity rate is 0.4 and the maximum temperature of the feed cabin is 47.56 ℃ at 12:00.Furthermore, the temperature of reflector surface reaches maximum 68.34℃ at 14:00, in which the minimum temperature is 35.03 ℃,and the temperature difference of reflector is 33.31 ℃. Moreover,the time domain of solar cookers is simulated.Finally,this paper gives the comments and suggestions for the design and use of FAST. The research in this paper not only obtains the temperature distribution of the FAST,but also provides references for the design and use of the FAST.