Abstract: A measuring device for the short-wavelength X-ray diffraction for test samples or work pieces made of lower-atomic-number crystalline and a method thereof are disclosed in the present invention. The measuring device comprises: an X-ray tube, an incident diaphragm, a table, a position-restricting receiving slit for a position-restricted part of a measured sample or work piece, a goniometer, a detector and an energy analyzer, the said X-ray tube and detector are arranged in the two sides of the table on which the sample or work pieces is located, the detector is intended to receive the transmitted diffracted ray. With the short-wavelength X-ray diffraction transmission method in the present invention X-ray diffracting patterns at different depths and different parts of a thicker test sample or work piece made of crystalline material and their distribution can be obtained without destructing the test sample or work piece, and then the data are processed by a computer to obtain phase, residual stress, etc.