Three-dimensional silica fiber reinforced silicon nitride composites were prepared by polymer infiltration and pyrolysis method using perhydropolysilazane (PHPS) and polyhydridomethylsilazane (PHMS), respectively. The microstructures of the composites were characterized by transmission electron microscopy. Strong fiber/matrix interfacial adhesion was observed for the PHPS-derived composites prepared at 1073K, and the PHMS-derived composites prepared at 873K without fiber precoating. While for the PHMS-derived composites prepared at 873K with fiber precoating, the coating changed the fiber/matrix interfacial bonding conditions, leading to high mechanical properties.