The present invention relates to a production method of high-purity lithium hydroxide. A crystallization mother liquor waste water is obtained after production of potassium chloride by using a salt lake bittern as the raw material, a magnesium-lithium ratio of the crystallization mother liquor waste water is 200-500:1, an eligible eluant is obtained through ion sieve adsorption and elution of the crystallization mother liquor waste water, and after treatment of the eluant through the ultrafiltration membrane technology, the sectional type nanofiltration technology, the external regeneration continuous hybridization technology and the reverse osmosis technology, a reverse osmosis concentrated solution is obtained. In the reverse osmosis concentrated solution, the content of magnesium ions is <=300 ppm, the content of lithium ions is 4-6 g / L, the content of sodium ions is 3-5 g / L, the content of calcium ions is <=5 ppm, the content of sulfate ions is 1-30 ppm and the content of boron is <=400 ppm. According to the production method provided by the present invention, the reverse osmosis concentrated solution is used as the raw material, the process comprises ultrahigh pressure reverse osmosis continuous hybridization for boron-removing, continuous hybridization for sulfate radical removing, ion-exchange membrane electrolysis, and crystallizing evaporation, and by using the hybridization boron-removing technology, the ion-exchange membrane electrolysis technology and the crystallizing evaporation technology, the high-purity lithium hydroxide is obtained, with the byproducts being the boric acid and sodium hydroxide. The process is continuous, controllable, high in extraction rate, low in production cost and easy to industrialize.