Olivine synthesized by wetness impregnation (WI) and thermal fusion (TF) methods were investigated as in-situ catalysts to reduce the tar content during air-blown biomass gasification in a circulating fluidized bed (CFB). The results showed that the tar content decreases with the increase of reaction temperature. Raw-olivine reduced tar content by 40.6% compared to non-active bed material (silica sand) experiments; after calcination, the catalytic activities of olivine catalysts were further improved due to the migration of Fe from olivine grain to the surface. 1100-WI-olivine could reduce the tar content by up to 81.5% compared with that of raw-olivine because of the existence of Fe2O3, NiO and NiO-MgO. For 1400-TF-olivine, due to the formation of NiFe2O4, the tar content decreased to 0.77 g/Nm(3), an 82.9% reduction compared to raw-olivine. Moreover, the TF-olivine had a stronger anti-attrition performance and was more suitable for using in a circulating fluidized bed.