Abstract: The distributions of activation energy of different hydrocarbon source rocks and the relationship between average activation energy and different macerals were discussed in this paper.Research results show that a positive correlation between maturity and average activation energy can be observed.The same is true of the content of vitrinite.The correlation between the content of lipinite and average activation energy have two kinds of trend.It is a positive correlation when the organic matters have been altered strongly by microbe,if not,there is a negative correlation.The correlation between the content of exinite and average activation energy shows a negative trend.The research confirms that activation energy of hydrocarbon source rock has many influential factors and its hydrocarbon generation principle is complicated.Algae have characteristics of inchoate hydrocarbon generation and they are important hydrocarbon sources of immature oil.The hydrocarbon source rocks which possess many kinds of maceral have characteristics of multi-period hydrocarbon generation.