This paper provides a software simulation model for performance prediction of a parabolic trough collectors system (PTCs), as a part of solar thermal power plants. The simulation has been carried out in Mathcad program environment using the equations, correlations and typical values of certain parameters available in the open literature in addition to methods from widely accepted reference materials and assumptions to the best ability. The software is carried out to predict the solar radiation intensity from sunrise to sunset, the DNI (Direct Normal Irradiance), PTCs parameters which include: heat losses factor (UL), collector efficiency factor (F’), and the heat removal factor (FR), optical efficiency ηop, temperatures, mass flow rate of heat transfer fluid (HTF), heat transfer to and from PTCs. The effects of the variations in some PTCs design parameters and operating conditions on the PTC solar field performance can be investigated such as the beam radiation incidence angle, the emittance of the receiver and glass cover using this software model. The calculations were limited to high-temperature oil (therminol VP-1) as HTF. The PTCs model is validated with the experimental and numerical results. Detailed design and simulation of PTC thermal power plant of around 108 MW was planned to be set up at Aswan, Egypt. For this proposed plant, the model was used to evaluate the solar field performance. The site with Mathcad simulation model of the article: http://twt.mpei.ac.ru/MCS/Worksheets/PTU/Math-Sun.xmcd