Polycarbosilane (PCS) was used as a precursor to prepare porous silicon carbide (SiC) ceramics with in situ growth of beta-SiC nanowires. The pore size of the as-prepared porous ceramics was 1.37 mu m in average, and had a narrow distribution. The nanowires with diameters ranging from similar to 10 to 50 nm existed in the channels of the porous body. Their morphology, microstructure, and composition were characterized by field emission scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy, which confirmed that the nanowires had a single-crystal beta-SiC structure with the < 111 > growth direction. A vapor-liquid-solid process was discussed as a possible growth mechanism of the beta-SiC nanowires.