Chalk degree is one of the most important indicators for judgment of rice quality. In order to quickly and objectively and accurately detect rice chalkiness, the purpose of this article is for the practical application. Firstly, the rice has been extracted from background with optimal threshold, then, after the optimal threshold of extracting chalk has been defined through contrast-ribbon approximating chalk, the chalk has been extracted from the rice. Chalky grain has been defined through Calculating area ratio of chalk and the whole rice, chalky area ratio and chalky grain rate have been cal...