Abstract: In the Niutitang Formation of lower Cambrian in the middle and upper Yangtze region in east Sichuan, west Hubei, and north and middle Guizhou, there occurs a thick sequence of marine argillaceous source rocks with high organic matter. Based on the analysis data and in accordance with the existing criteria for assessment of marine source rock, a comprehensive study was carried out by the authors. The results indicate that the organic carbon is high in the deposits, above the standard of good or better quality of source rocks. Almost all the organic matter belongs to Type I. The Ro of the source rock is higher than 2.0% with an average of 3.15%, suggesting that the source rocks have reached an over-matured stage. In this regard, gas should be the first priority in hydrocarbon exploration in this region. The black argillaceous rocks widely distributed in the region should be selected as the exploration target for shale gas.