Solar Parabolic Trough Collectors (PTCs) are currently used for the production of electricity and applications with relatively higher temperatures, these technologies offer a real alternative to the fossil resources with a little or no environmental impact. In this study, the potential of direct solar irradiance in Egypt and the performance of solar parabolic trough collector (PTC) are estimated under the climate conditions of the country. These two factors are treated as they play an important role in the design of solar thermal plant. In order to determine the most promising solar sites in Egypt, monthly mean daily direct solar radiation have been estimated and compared for different locations corresponding to different climatic region.The study is based on a mathematical modeling of the PTC. Heat balance has been established respectively on the heat transfer fluid (HTF), the absorber tube and the glass envelop using the principle of energy conservation at each surface of the HCE. At first the results for typical days of two seasons; the thermal behavior of the HTF, the absorber and the envelope are obtained. Then to determine the thermal performances of the parabolic trough collector PTC, molten salt (Solar salt) is considered and its temperature, heat gain and other thermal properties evolutions are compared under the topographical and climatic conditions. This analysis is performed with advanced numerical system model which is the system model advisor (SAM) model developed by NREL.