Novel solar thermal desiccant cooling system has been developed. Experimental operation and evaluation of the system was conducted. System optimization and parametric investigation are so important for the improvement of system performance. However, inasmuch as evaluation through experimentation is time consuming and very expensive, numerical model is made and developed for the system. The developed model is implemented in TRNSYS program. The model is validated using the experimental data of the system. Based on the result of the numerical evaluation is conducted the area of the installed solar collector area must be reduced to 8m2. The needed electric heater heating operation is 2 hours. Reduction of the solar collector inclination angle to 30° improved the solar energy collection. Improvement of the desiccant wheel dehumidification rate increased the system total performance. Increasing the heat exchanger (HEX 2) efficiency lowered the supply air temperature with improvement of system performance. Reduction of the system electric energy consumption increased the system electric COP (ECOP). These results of the study are of great importance for the improvement of the design of the developed system, operational procedure, and performance. The relationship and effects of the variables in the study are applicable for other researches seeking the effects of the operational parameters for the solar thermal desiccant cooling system design and processes.