In this experimental work we studied the effects of fuel-to-air velocity ratio and air flow blockage ratio on the reacting flow pattern, thermal structure, and flame features in a bluff-body flame stabilizer. Spatial and temporal distributions of temperature and streamlines were measured by very fine thermocouples and LDV, respectively, and PLIF-OH image was also analyzed. The results show that all flame zones were controlled by the recirculating flow upstream, which was formed by interaction between the concentric jets. Spatial and temporal data of temperature and velocity fluctuations and images of hydroxyl radical concentration in the flow reveal a closed relationship between combustion and transient behavior of fluid dynamics. The large-scale motion of the recirculating flow played a determining role in the mixing, reaction, and stabilization in the entire flame area. Moreover, the velocity ratio and blockage ratio are both important factors to induce the position change of the high temperature reaction zone. The position of the reaction zone will move upstream from the outer shear layer of the air-driven vortex while the velocity ratio increases, and finally transfer to the inside area of the recirculation zone. The phenomenon becomes more apparent as the blockage ratio gets larger.