Abstract: Based on the irreversibility of compacted argillaceous rocks and the controlling effect of lithologic composition on under-compaction, a new method of dynamic analysis for the interpretation of compaction curves is proposed. With this method, under-compaction curves may be segregated into compaction curves of different types and trends of later compaction for under-compacted argillaceous rocks may be predicted. Besides, the conclusions drawn thereby about the depth and direction of expulsion of hydrocarbons and appraisal of source rocks are different from those by static analysis in many ways. Compaction curves are classified into three kinds. They may be used for forecasting and appraising of oil prospects readily.