Yttrium-barium cuprates are of a great interest due their possible application in the manufacture of superconductors and devices on their basis. This paper shows the possibility to synthesize ultrafine powder of yttrium-barium cuprates using the system based on a coaxial magnetoplasma accelerator. Several methods, including X-ray diffractometry, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy, are used to investigate the synthesized products. It is found that during working cycle with a duration less than 1 ms, all necessary conditions are created to synthesize the powder with the stoichiometries YBa2Cu3O696 and YBa2Cu4O8. These materials can be used for sintering the multilayer ceramics using the system of spark plasma sintering.