There is abundant natural gas but less oil accumulation in Palaeozoic and Triassic marine reservoirs in the east part of Sichuan Basin. Recently, some yellow greenish light crude oil show was discovered in fissures of marine Lower Permian Maokou limestone at Moxinpo Coal Mine in Chongqing. The oil has been analyzed by a series of geological and organic geochemistry methods. The distribution of n-alkane in aliphatic fraction of the oil ranges from n-C4 ton-C26 with obvious pristane preference (Pr/Ph=1.64). Relatively high Ro (about 1.6,) of the calculated oil maturity is consistent with the measured vitrinite reflectance of the Permian coal at Moxinpo. The δ13C is -26.2‰, which is similar to those from Permian Longtan shale and coal. It is considered that the oil in limestone fissures is mostly derived from the marine Permian coal measure strata, including some contributions of continental organic matter. The accumulation of the hydrocarbon needs to be further studied. The discovery of the oil show hints possible industrial hydrocarbon accumulation in some relative low mature reservoirs among high mature areas of Sichuan Basin.