Carbonate rocks are able to source rocks that supply rich hydrocarbon for reservoir but not all of carbonate rocks can be as source rocks. In the process of hydrocarbon accumulation, carbonate rocks commonly act as carrying beds or reservoirs and are interfered easily by allogenic organic matter. It is considered that carbonate source rock should be a place holding organic matter (combined with minerals asa part of sediments) and is of a certain abundance. Hence as a result, liquid and gaseous hydrocarbon would be generated if the carbonate rock is during a appropriate thermal-mature stage. Carbonate rocks generally develop in low-energy environments of sedimentary facies, such as open sea platform, restricted sea platform, biomudlump and slope facies. Pelitic micritic limestone, biomarl-wackstone and packstone microfacies should be the hosts of carbonate source rocks. Comparing with oil-rich argillaceous source rocks, the carbonate rocks are characterized by evident oil window phases with peak ahead-migrating, unobvious peak phases of gaseous hydrocarbon with peak back-migrating, and high-yield liquid hydrocarbon. According to the assessment of potential hydrocarbon quantity in Sichuan Basin, carbonate rocks contribute 20,~25, of hydrocarbon quantity to source, which play an important act to hydrocarbon accumulation in the basin.