The membrane fouling is one of the key issues in ultrafiltration (UF) process because it significantly reduces the membrane permeability and increases industrial cost. The challenge is to improve antifouling ability of UF membranes without compromising their separation performance. Here we report a facile strategy to prepare antifouling UF membranes via grafting of positively charged poly(ethylenimine) (PEI) chains onto brominated tetra-methyl polyethersulfone (TM-PES) membranes. The resultant PEI grafted TM-PES membranes show excellent antifouling ability with sufficient water permeability and outstanding separation performance. Typically, the grafted membrane with the bromination degree (BD) of 73% has not only a high water permeability of 72 Lm(-2) h(-1) bar(-1) but also rejections of 96.3% for ferritin and 91.4% for bovine serum albumin (BSA). Specially, the water flux can be recovered nearly 90% after protein fouling. The developed strategy is suitable for preparation of antifouling UF membranes. Moreover, the fabricated membranes have a great potential application in biomacromolecule separation.