Abstract: The radiation heat transfer and evaporation characteristics of high temperature liquid droplet flow in the liquid droplet radiator were studied under the condition of vacuum and weightlessness in this paper. On the basis of the traditional radiation heat transfer model of high temperature liquid droplet flow, the evaporation model of liquid droplet flow was added, and the radiation heat transfer model was coupled with the evaporation model, then the analysis code LDFAC was developed. The relative error between the code simulation result and check value is less than 1.9%. This code was used to analyze and calculate the radiation heat transfer and evaporation characteristics of droplet layers with different optical thicknesses or length loaded with DC705 silicone oil. The results show that the temperature distribution of the thick droplet layer is uneven, and the temperature has a great influence on the system life of droplet radiator, the system life can increase by about 450% for every 10 K decrease in temperature.