Abstract: A type of micro X-ray diffractometer and its hardware, software, and performances were introduced in this paper. In this diffractometer, polycapillary X-ray optics was employed to focus the X-ray beams down to micron size. The closed-loop controlling system composed of PLC and stepping motors controlled the movements of three-dimensional sample stage. This structure could help to accomplish the analysis of crystalline phase in micro area and its mapping in two-dimension. Moreover, the two measurement modes of micro energy dispersive X-ray fluorescence (μ-EDXRF) and micro X-ray diffraction (μ-XRD) were designed in our software. In order to test the feasibility of this diffractometer, an area of 1.0 mm×0.6 mm on the surface of a solder contact point in an iPhone mainboard was scanned by the method of micro X-ray diffraction. The phase mapping of SnO₂ (3 1 2) in this area was acquired by data processing. Furthermore, the main crystalline phases of the white glaze and pigment on a piece of red and green porcelain produced in Qing Dynasty were investigated by this diffractometer. It detected several mineral phases of orthoclase and anorthite, etc. These results could provide useful reference information for the firing process of ancient porcelain. In the conclusion, this micro X-ray diffractometer has a wide application prospect in the fields of materials science and the protection of cultural heritage.