The Qinghai-Tibet Plateau is located in the east section of the Tethys region, which produces great amounts of oil and gas whose reserves are one of the most abundant in the world. The plateau includes two exploration areas: a Mesozoic marine basin and a Cenozoic continental facies. At present, the Qiangtang Basin in the Qinghai-Tibet Plateau is believed to be the marine basin with the most extensive oil and gas exploration prospects in the world; however, the thrust-nappe structure movement in the Cretaceous-Cenozoic Period caused massive surface exposure which damaged the oil reservoirs. In this paper, the paleo-oil reservoir exposure area was used as a window to reveal the massively exposed underground distribution of oil and gas reservoirs in the Southern Qiangtang Depression, and the reservoirs were analyzed in detail. The composition of biomarkers and the characteristics of carbon isotopes of crude oil in the reservoirs were identified via comparison of oil source rocks. Our findings indicated that the oil shale series source rock from the Biluocuo region of the Qiangtang Basin represents the main source rocks of the paleo-oil reservoirs.