Cooling towers make use of evaporation whereby some of the water is evaporated into a moving air stream and subsequently discharged into the atmosphere. As a result, the remainder of the water is cooled down significantly. The process parameters such as inlet air rate, water flow rate and fills porosity have more influence on Thermal performance of cooling tower. The Temperature of outlet water is maintained nearest to inlet air wet bulb temperature to obtain the best Thermal Performance of cooling tower. So current work is to obtain and maintaining outlet water Temperature nearest to inlet air wet bulb temperature. The cooling tower fill is the most critical component in the operation of the cooling tower. The function of the tower fill is to provide a maximum contact surface between the water and the air to promote evaporation and heat transfer. Cooling tower fill accelerates the transfer of heat from circulating water by maximizing the contact area between water and air. So inlet water flow rate, inlet air rate and fill porosity are important factor to maintain the outlet temperature of water nearest to inlet air wet bulb temperature.