To study total reservation and distribution of oil and gas in the sedimentary basin, the distribution of source rock should be investigated first. Based on the limited number of core samples, it is impossible to obtain the continuous laboratory measurements of organic carbon of source rock. The full information of organic carbon can not be revealed by laboratory measurements, because it is the geometric mean value of several discrete core samples. Well logging evaluation of source rock is carried out in order to get the information about continuous organic carbon content and thickness of source rock. In Shahejie Formation, source rock is identified by typical well logging characteristics of high gamma, high porosity, and high resistivity. The continuous organic carbon content of source rock is calculated by using a quantitative relationship model, which is established based on multivariate statistical analysis between well logging information and the core carbon content. Comparing with different methods for organic carbon content calculations, the Passey formula method is found to fit well with the core geochemistry method, and with a small relative error. The Passey formula method is basically confirmed that it satisfies the demand for hydrocarbon source rock evaluation in Bohai Bay oilfield. The processing results of 20 wells indicate that there is higher organic carbon content and thicker source rock in Shahejie lacustrine Formation. Especially, the middle of the third zone of Shahejie Formation is the most beneficial layer of source rock.