A modified PES ultrafiltration membrane with excellent separation and antifouling properties was obtained after modification by remote Ar–NH3 plasma-induced acrylic acid (AA) grafting. Hydrophilic properties were characterised using water contact angle measurements. The morphology was analysed using SEM and BET measurements. Changes in the surface functional groups were determined using XPS and ATR-FTIR. The separation and antifouling properties were evaluated through a bovine serum albumin (BSA) separation experiment. The results revealed that the surface structure of the modified membrane was not destroyed, that amino groups were introduced on the surface of the PES membrane, and that AA was successfully grafted. The water contact angle decreased from 67° in the original membrane to 5 ± 0.63° in the modified membrane. The water flux increased from 30 to 93.6 L/(m2·h). The rejection rate of BSA increased from 61.5 to 93.8%, and the flux recovery rate increased from 60.0 to 92.3%.