The photoacoustic spectra from ptype αporous silicon carbides prepared under UV photoassisted process and under darkcurrent condition have been measured，the original silicon carbides were also measured. Combined with RosencwaigGersho theory, the photoaconstic spectra are turned into the absorption spectra. It is found that the energy band gaps of the porous silicon carbide were lower than that of the original silicon carbide, and the causes were analyzed in detail. The absorptions near the absorption edge were studied as well.