Biomorphic silicon nitride (Si3N4) ceramics with fibrous morphology were fabricated by combining sol-gel infiltration with carbothermal reduction nitridation from wood precursor. Y2O3-incorporated silica sol was used as the infiltrated solution to promote the formation of fibrous Si3N4 grain at 1600 degrees C under high nitrogen pressure (0.6 MPa). The influence of sintering conditions (additive and temperature) on the phase composition and microstructure of sintering bodies was analyzed, and the reaction mechanism is discussed.