The main objectives of this project are to develop a simulator that represents Al-Hail Reverse Osmosis plant and to compare results obtained from the developed simulator with the real data. This simulator can be then considered as a first step in constructing an on-line monitoring and controlling system of the Al-Hail Reverse Osmosis plant. In this project, a simulator for the Al-Hail Reverse Osmosis plant is developed using engineering software called "LabVIEW". LabVIEW is commercial computer application software, which is much like National Instruments Lab Windows/CVI, but it is different in terms of using graphical programming language (G) to represent the system components in the form of block diagram, rather than text. It works with all aspects of instrumentation systems including data acquisition and control, data analysis, and data presentation. A series of equations and relationships of the Al-Hail Reverse Osmosis plant is programmed in LabVIEW. About 88 generated output variables are calculated from running the developed simulator with 10 input variables. For validation purpose, the comparison between the real data from the Al-Hail Reverse Osmosis (RO) plant and the developed LabVIEW simulator is performed with respect to some variables and concluded that the obtained results reveal good prediction to some extent.