In current scenario, there is an increasing need to have faster product development and achieve the optimum design quickly. In an automobile air conditioning system, the main function of HVAC third row floor duct is to get the sufficient airflow from the rear heating ventilating and air-conditioning (HVAC) system and to provide the sufficient airflow within the leg locations of passenger. Apart from airflow and temperature, fatigue strength of the duct is one of the important factors that need to be considered while designing and optimizing the duct. In the vehicles having third row seat, floor duct is connected to the rear HVAC and it is routed under the seat below the carpet to provide the airflow. Passenger would keep the luggage in the third row carpet area by unfolding the seat and there is a chance that passenger might walk over the duct routing carpet area. Due to the overloading of luggage, duct might get damaged or deformed. The challenging task is to package the duct below the carpet within the constrained space and the duct should withstand the load applied by the passenger leg and the luggage. It is very important to do the stress and deformation prediction through 3D analysis before finalizing the optimized design. Finite element analysis (FEA) has been used extensively to validate the stress and deformation of the duct under different loading conditions applied over the duct system. In this paper, the focus is to optimize the third row floor duct design to withstand the maximum loading conditions with minimum stress level and deformation. It is good to establish an accurate FEA modelling technique and analysis procedure that simulates the loading test conditions. The input for the analysis is the force acting on the duct at different locations maintaining at the room temperature. The result predicted is the stress distribution throughout the duct and deformation at load acting locations. Multiple FEA simulations have been carried out for various design concepts to finalize the best optimized design. Proto parts were made for the optimized design and loading test was carried out in the test bench to know the stress distribution and whether deformation is happening or not when the load is applied over the duct at different locations. There is a good correlation between test and simulation results within the error of 7%. Successful validation of the simulation process has led to the application of this methodology in the pre-production stage of new programs during the design phase. This simulation methodology helps in finding out stress and deformation results of the duct in the design stage of the program and aids in reducing the physical testing iterations.