This research is aimed at geometric analysis of parabolic trough solar collector (PTC) in different sizes of the main components of the system. The rate of the Local Concentration Ratio (LCR) on the receiver tube and optical efficiency are two main features in geometric optimization of the parabolic trough solar collectors. In this work, parabolic trough solar collector was optimized for different sizes with three design variables: the receiver diameter, the collector aperture width and the rim angle. The method used in this research was the Monte Carlo Method (MCM) in MATLAB. The optical and geometric modeling was developed for coding in MATLAB. For the case study, a parabolic trough solar collector was used in the laboratory. The current results showed that the optical efficiency of 65% was obtained for the collector components with the collector aperture width of 0.6 m, rim angle of 100° and receiver diameter of 0.025 m. Also, the optical efficiency of 61% was obtained for the collector with the aperture width of 0.7 m, rim angle of 90° and diameter receiver of 0.025 m. © 2018 Elsevier Ltd