This paper presents four theoretical fundamentals of the application of changes of diagenetic parameters in the study of tectonic activities. For the first time tectonic movement, lithology and diagenesis are closely related together. The structure-lithofacies theory holds the view that tectonic movement controls the distribution of lithofacies, and the authors believe that diagenesis varies with the lithologies. Erosion or meteoric leaching caused by tectonic elevation may exert certain influence on diagenetic parameters, and local structural activity may also lead to the difference in diagenetic degree of rocks in the same horizon. On the basis of the abrup't changes of some parameters and the great difference of diagenesis, the authors infer that tectonic activity might have occurred. This is in good agreement with the study of diagenesis of the following strata: (1) the Jurassic in Shanle oilfield, Turpan-Hami Basin, (2) the Eogene in the Dongpu depression, (3) the Eogene Dongying Formation in JZ20-2 structure, Jinzhou, Liaodong Bay area, and (4) the Neoproterozoic Xiamaling Formation in Pingquan, Hebei Province.