The drastically increase in energy demand and the problems resulted from environmental pollution have led to a serious trend towards energy utilization efficiency improvement through scientific researches related to renewable energies, particularity that Syria has a high solar irradiance and prolonged sunshine hours. This research focuses on determining the thermal efficiency for a prototype of a parabolic trough solar concentrator (PTC) to obtain the optimal prototype thermally and economically according to climatic conditions in Damascus. It has been deposited the mathematical model of the studied concentrator depending on the calculated design parameters through calculating the solar angles equations and direct solar irradiance throughout the year. And it has been solved this model by using numerous computer programs (Excel, EES).