A method for processing bast-fiber materials involving loosening a material, placing said material in an aqueous medium, hydrodynamically processing material successively in two modes: first, in a continuous mode by performing a hydrodynamic wave field action, and then in a pulsed mode by performing a shock-wave action, wherein the pressure amplitude of the positive wave phase in the continuous mode is less than the pressure amplitude of the positive wave phase in the pulsed mode, and removing the material from the aqueous medium. It is possible by the method to produce a high quality cottonine, the linear density of which is equal to or less than 0.3 Tex with the optimal energy consumption of the production process.