Abstract: Theoretically, the Differential Strain Analysis (DSA) method based on solid theory is widely used in in-situ stress measurement, but the application of the method is restricted by the rigorous and complicated experimental conditions and test procedures. In view of the present situation, based on the DSA method and the technique of palaeomagnetism orientation, the theory about the wave velocity anisotropy and the orientation of stress is introduced to the DSA test, a new method named the principal direction DSA method is developed to make the laboratory test simple and feasible. According to the distribution characteristics of the rock wave velocity, the method is used to determine the orientation of the principal stress horizontally, based on which DSA core samples are prepared for the test. Compare with the conventional DSA method, the relative error of the magnitude of in-situ stress using the new one is less than 3%, and the error of the orientation of in-situ stress is less than 5o. The case study indicates that the method decreases the technical difficulty of test dramatically, and its accuracy meets the requirement of engineering technologies, so it deserves to be popularized.