Based on the examination of the losing of organic matter due to the generation and expulsion of hydrocarbons and the weight loss of inorganic matter due to diagenesis and water expulsion, this paper presents calculations of the variations of organic matter abundance and hydrocarbon-generating potential along with changes of the organic matter type, the initial organic carbon content, the maturity degree and hydrocarbon expulsion efficiency in the geologic history; and discusses the possible variation ranges of the restoring coefficient of organic carbon and the loss ratio of hydrocarbon potential. The results indicate that the variations of organic matter abundance and hydrocarbon-generating potential during geological processes depend mainly upon the efficiency of hydrocarbon generation and expulsion. For type I organic matter, the measured content of organic matter increases rather than decreases with the deepening of evolution, whereas for type I organic matter, the restoring coefficient of organic carbon can be as high as 2. The loss ratio of hydrocarbon potential increases with meliorating organic type and increasing maturity. Generally speaking, the restoring extent of hydrocarbon potential of organic matter is much higher than that of organic carbon.