Abstract: In order to deepen the research of hydrocarbon accumulation process and identify the principal source rocks of Pingbei Area in Xihu Depression, hydrocarbon generation history and expulsion history in the study area are reconstructed quantitatively by dynamic numerical modeling of the petroliferous basin based on the analysis of source rock distribution characteristics, organic matter abundance, types and maturation. Two source rock system.s are revealed in the study area: Pinghu formation and Huagang formation. Pinghu formation is the principal one, which has a high organic matter abundance and maturation, hydrocarbon generation-expulsion intensity and hydrocarbon expulsion efficiency. It is suggested that the petroleum system in Pinghu formation should be the major exploration target in the study area.