The invention discloses a concentrating method of high-selenium water. The method includes: collecting natural selenium-enriched water; filtering the natural selenium-enriched water; concentrating the filtered natural selenium-enriched water with reverse osmosis equipment, separating pure water in the selenium-enriched water, and collecting concentrated water discharged from the concentrated water outlet of the reverse osmosis equipment; repeatedly concentrating the collected concentrated water with the reverse osmosis equipment until the high-selenium water with the selenium content meeting application requirements; sterilizing, detecting and storing the high-selenium water. The concentrating method has the advantages that the common natural selenium-enriched water can be concentrated into the high-selenium water by the reverse osmosis technology, and the concentrated high-selenium water is mainly used for being added into food to allow the food to meet the selenium content requirement of selenium-enriched food.