Corrosion experiments were conducted in a 0.4 T/D circulating fluidized bed (CFB) test rig with the high-sodium high-chlorine lignite as fuel to investigate the corrosion phenomena and mechanisms through the air-cooled probes in furnace and tails, respectively. Three alloy materials involving four metal elements (Al, Cr, Ni, and Fe) were used to compare their anticorrosion characteristics with the thermodynamic equilibrium calculation software Factsage 6.1 as an auxiliary tool. Experimental results indicate that the probes exposed to the high-temperature flue gas in the furnace suffered severe corrosion, which was primarily caused by gaseous corrosive media, including HCl (g), NaCl (g), and Cl-2 (g), while the probes in tails underwent the almost negligible corrosion arising from the deposited NaCl crystal on the top surface of the probe. The protective oxidation scale formed on the outer surface of alloy was the key to corrosion resistance rather than the internal metal with high quality. Despite different alloy elements matching different corrosive environments for its optimal anticorrosion, the Al2O3 was found most effective to resist the chlorine-induced corrosion in this study. In accordance with the Gibbs free-energy change (Delta G) of corrosion reactions, the increasing temperature failed to reduce the difficulty of corrosion in essence. The accelerated corrosion at a higher temperature was mainly ascribed to the improvement of the diffusion of the gaseous corrosive species and gaseous reaction products (metal chlorides). At a low-level wall temperature, to a certain extent the influence of gas temperature and alloy materials on corrosion can be ignored.