Abstract: The system for in-situ real-time measurements of microstructure properties of 3D-printing objects during 3-D printing processes. An intensive parallel X-ray beam (with an adjustable beam size) impinges on a printing object and is diffracted on a crystal lattice of the printing material. The diffracted radiation impinges on a reflector formed with an array of reflector crystals mounted on an arcuated substrate. The diffracted beams reflected from the reflector crystals correspond to the diffraction intensity peaks produced by interaction of the crystal lattice of the printing material with the impinging X-ray beam. The intensities of the diffraction peaks are observed by detectors which produce corresponding output signals, which are processed to provide critical information on the crystal phase composition, which is closely related to the defects and performance of the printing objects.