Abstract: A core from a certain depth is marked with a master orientation line (MOL), and is made into standard samples, which are used in palaeomagnetic tests and differential strain analysis (DSA) in the laboratory. The original orientation of the core in the formation can be obtained by magnetic cleaning test, magnetic parameter measurement and data processing. Differential strain analysis (DSA) method, which is used to determine the direction of the maximum principle stress with respect to the master orientation line, is combined with the results of magnetic tests to define the direct of the maximum principle stress in the area.