The invention discloses a device for evaluating performance of a forward osmosis membrane. The device comprises a raw material liquid tank, a feed liquid pool, a forward osmosis membrane component, a draw solution pool, a high-concentration salt pond and a delivery tank, wherein a check valve and an overflow pipe are arranged on an overflow tank of the pool; an aeration pipe is arranged at the bottom; the forward osmosis membrane component comprises a shell; a forward osmosis membrane is arranged inside the shell, and divides the shell into upper and lower lattices, which respectively are a draw solution chamber and a feed liquid chamber; the draw solution chamber is put into a magnetic stirrer; a water inlet/outlet of the draw solution pool is connected with the draw solution chamber of the forward osmosis membrane component; a probe of a conductivity controller is put into the pool; the water outlet of the high-concentration salt pond is connected with the water inlet of the draw solution pool through a pipeline with a strong brine pump; opening and closing of the strong brine pump are controlled by a conductivity meter; the delivery tank is put on an electric scale. The device disclosed by the invention is small in volume, simple and easy to operate, stable in test result, small in required area of the forward osmosis membrane, wide in application range, and applicable to test of the forward osmosis membranes with kinds of sources.