Abstract: The level of pressurization during hydrocarbon generation directly affects efficiency of hydrocarbon expulsion from lacustrine source rocks. In this study, a simulation experiment is conducted for quantitative analysis of pressurization during hydrocarbon generation from lacustrine source rocks. Major factors that control this process are identified and discussed. Maximum of pressurization during hydrocarbon generation is approximately 54% of overlying lithostatic pressure, indicating that hydrocarbon generation pressurization is the primary driving force for hydrocarbon expulsion from lacustrine source rocks. The degree of thermal evolution, type and abundance of organic matter show positive effects on pressurization during hydrocarbon generation. Under the same experimental conditions, the higher grade of organic matter type, the stronger effect of abundance of organic matter on hydrocarbon-generating pressurization; the higher abundance of organic matter, the stronger influence of organic matter type on hydrocarbon-generating pressurization. In contrast, lithostatic pressure plays a negative role in pressurization during hydrocarbon generation.