This study suggests a theoretical performance study of an existing solar Parabolic Trough Collector (PTC). A study of the trough thermal analysis is necessary to evaluate the performance of a PTC. The parametric study of the existing PTC makes use of the mass flow rate, the concentration ratio, the different Heat Transfer Fluid (HTF), the solar insolation and the heat removal factor. The results showed that the efficiency of PTC decreases for various mass flow rates and HTF, as the inlet fluid temperature increases. This is because the radiation losses increased as the collector temperature increases. It is also observed that the useful energy from the PTC decreases for various concentration ratios and insolation, as the inlet fluid temperature increases.