During working in field,the author has often seen some faults with steep dip angle which appear the form of normal fault but have the squeezed feature.The stress action way mirrored by the faults is contrary to regional stress field.Based on the functions of mechanical properties of rock bodies and their changes in tectonic activities,these contradiction phenomena are discussed.The mechanical properties of rock mainly include the gravity of rock body and the stress relaxation,and the author considers the relaxation in rock is caused by both aspects of rheology and non-rheology.Based on the idea,the relations between these factors and seismic activities are discussed,and some practical tectonic phenomena also are analysed.