The invention belongs to the technical field of desalination of sea water, and discloses a method and system for realizing sea water desalting through hot film coupling self circulation. The method comprises the following steps of performing multiple-effect evaporation on water to be desalted through a multiple-effect evaporation technology, and outputting condensation water, distilled water and primary strong brine; performing hardness removal pretreatment on the primary strong brine for removing calcium ions and magnesium ions, so as to output hardness removal water; performing treatment on the hardness removal water through a reverse osmosis film, and outputting desalted water and secondary strong brine; introducing the secondary strong brine into the water to be desalted, and performing after-treatment through the multiple-effect evaporation technology; and repeating the above steps so as to realize hot film coupling self-circulation treatment. The invention provides a raw material which can reduce desalination energy consumption and can output high-quality salinized industrial products.