In this paper various classifications of diagenetic stages are discussed and grouped into five schemes. The authors hold that it is most reasonable to divided diagenesis into syndiagenesis, anadiagenesis and epidiagenesis. The classification into syngenesis, diagenesis , epigenesis and ep-idiagenesis is also suitable in consideration of the actual situation in China. The two classification schemes reflect the present level of diagenesis research. The authors review all terms of diagenesis which are confused in comprehension and usage now and present a comparative table of main schemes of classification of diagenesis.