In this study, the fuel-lean reburning system is considered for reducing NOx emission by using an experimental and numerical approach in conjunction with a lab-scale furnace. Liquefied petroleum gas (LPG) is used as the main and reburn fuel. The goal of this work is to obtain the most optimal combustion system by employing the fuel-lean reburning system to reduce environmental pollution. The amount of reburn fuel and injection location of reburn fuel are considered as experimental parameters. There are very few studies that have focused on how the reburning process is affected by changes in the flow field that are induced by combustion. It is important to study the effect of the combustion condition on the reburning process in order to control fuel-lean reburning. A computational fluid dynamics (CFD) model is used to provide understanding of the complex combustion phenomena. The validation of the predicted results is carefully conducted by comparing the predicted results with the measured data such as species concentration and temperature distribution inside the furnace region. The measured results show that the fuel-lean reburning method leads to 50% NOx reduction by using a ratio of reburn fuel to total fuel of 0.13 and by achieving complete combustion without any additional oxidizer. In addition, predicted results indicate that the recirculation flow into the furnace region is carefully considered in order to enhance the reburning efficiency.