Blast furnace (BF) dust can be recycled as one of excellent secondary sources, in view of the valuable amounts of iron and carbon contents, and the in-flight reduction technology is considered to allow processing the fine metallurgical dusts efficiently. In this work, the reduction behavior of BF dust particles during in-flight process was studied using a high-temperature drop-tube furnace in laboratory scale. The effects of temperature and gas composition on the reduction degree were remarkable. Based on the morphological observation and phase diagram analysis, the product layer of the reduced BF dust particle was confirmed in molten state at 1673-1723 K. Kinetic analysis showed that the gas-molten particle reduction during in-flight process was a mixed control of the chemical reaction and diffusion of Fe3+ and O-2(-) ions through the molten product layer, and the corresponding chemical reaction constant (kr) and the diffusion coefficient (D) was also obtained.