The invention relates to a forward osmosis concentration system. The system comprises a seawater pretreatment clarifying tank, a first circular draw-off pump, a multistage draw solution evaporation regulating tank, transparent glass, a second circular draw-off pump, a secondary filtration device, a draw solution storage tank, a draw solution injection pump, a concentrated liquor draw-off pump, a concentration tank, a concentrated liquor injection pump, a forward osmosis device, a draw solution draw-off pump, a third circular draw-off pump, a water collecting pipeline and a water collecting tank. Water in raw juice is driven by osmosis pressure in the system to enter a draw solution through a forward osmosis membrane, thus realizing the concentration of the raw juice; the diluted draw solution can be evaporated into a high-concentration draw solution through a seawater baysalt technology, and is delivered back to the forward osmosis technology again as a draw solution, thus the high-efficiency cyclic utilization of the draw solution is realized, the engineering construction cost and the running cost are greatly reduced, and considerable economic benefits are achieved.