The reliability parameters of a Mathematical model are analyzed for a system with three identical units and a standby. In this study, the primary unit is considered more important due to its high cost and working in two types of degraded conditions before a complete malfunction. Under the concept of preventive maintenance, the states of deterioration are reversed. The working of the system under two different efficiencies is discussed. The reliability of the Mathematical model, depending on the availability and working time, has been optimized using the Mathematical tool “Genetic Algorithm”. The optimum values of all parameters based on the exponential distribution are considered to optimize the reliability, and thus provide maximum benefits to the industry. Sensitivity analysis of the availability and the working time is carried out to understand the effects of changing parameters. Graphical and tabular analyses are presented to discuss the results and to draw conclusions about the system’s behavior.