Abstract: The previous studies indicated that the widespread bitumen of the Sinian Dengying Formation in the central Sichuan Basin were epigenetic reservoir bitumen, which originated from the cracking of oil to gas in paleo oil pools and sourced from the Lower Cambrian mudstones. However, the original coexisting bitumen were also found in the Sinian Dengying Formation in the central Sichuan Basin, which could not be explained by the above opinion. Through the restudy of bitumen occurrence under microscope, biomarker characteristics and bitumen content, combined with the analysis of carbonate inorganic microelement, it was concluded that some of the bitumen came from the carbonate source rocks in the Dengying Formation, and the carbonate rocks in the Dengying Formation were qualified for favorable source rocks in paleo sedimentary environment and preservation condition.