Abstract: The method of treating the flax fibre consists of cleaning, cottonisation, retting and drying of the raw material, which could be short flax fibre No 2, combing wastes and other wastes. The opening of the flax fibre is carried out 3 times: first before the cleaning, second before the retting, and third after drying, which is done after cottonisation. This is carried out by means of electro-hydraulic treatment to a processed material placed in a liquid. This invention allows for quality improvement of the flax fibres and simplification of the processing.