Cavity profile and its parameter is an important aspect in supercavitation experiment, series of slender-body cavity flow pattern and control channel experiments were studied in high-speed tunnel. The cavity image information was obtained on the basis of high-speed photography, by further optimization of cavity image; the complete cavity information was given to provide valuable reference on study cavitation phenomena. In the article, image processing techniques was introduced in the cavity post-processing, by way of cavity image preprocessing; features extraction and identification, the valuable cavity information was obtained.