In the structural geology,we have long continued to use the method of C.M.Nevin to determine the stratigraphic duplicate and incompletement caused by the strike fault,the method is complicated and trivial.So using the following law could make it simpler than before:if the stratum of the upthrown side raises up on the strike fault,the surface stratum is incomplete,on the contrary,if the stratum of the upthrown side slopes down,then the surface stratum is duplicated.