Abstract:When plane elastic P-wave or plane elastic SV-wave or both project slantingly on a plane interface between two solid media,there occur reflected P-wave,reflected SV-wave,transmitted P-wave and transmitted SV-waveo In many old literatures,equations and matrixes describing the amplitude relations among these waves are different from each other in their forms because the wave function attributes,positive wave displacement directions,coordinate systems and parameters which are used in these literatures are different from each other,The stress of the paper is to discuss the relationship between the positive displacement and the coordinate system,P-wave displacement is a polar vector,and its direction remains unchanged when we move it from right hand coordinate system to left hand coordinate system (or in the apposite way).SV-wave displacement is an axial vector,and its direction changes with the change of coordinate system,The authors of old literatures took different coordinate systems in discussing the problem,causing different signs(+or-)of SV-wave items.For the convenience of use,it is proposed that right hand coordinate system should be used in seismic exploration.This paper uses right hand coordinate system,and presents equations and matrixes for displacement potential amplitude and displacement amplitude,namely,Knatt's equations,Zoeppritz equations and the corresponding matrixes.