Abstract: Based on the study made on the sedi-diagenetic characteristics of clastic sedimentary rock bodies with different types,sedimentary system and geological ages from different oil-gas bearing basins in the country,the authors proposed some new concepts about sedimentary systems and their classification,established the structural framework of sedi-dia-genesis,therefrom obtained diagenetic variables which reveal the paragenetic lows for the diagenetic sequences between clastic sedimentary rock bodies,paragenetic association of diagenetic minerals,and diagenetic facies and circles,and porosity decreasing or increasing,and their relationship with oil and gas.The study will effect to certain extent on improving the research of diagenesis and oil/gas prediction.