Nanofiltration membranes with excellent anti-fouling properties were fabricated through a green surface crosslink method. Poly (styrene-maleic anhydride) (SMA) blended polyethersulfone (PES) membrane was used as a support. The SMA in the PES support served as a macromolecular crosslinker. After coating of polyvinyl alcohol (PVA) on the surface of the SMA-PES support, a PVA selective layer with gradient crosslinked structure was formed, through the esterification between the anhydride groups in SMA and the hydroxyl groups in PVA. This process adopts a full-water fabrication strategy without secondary pollution. The gradiently cross-linked PVA/SMA-PES membrane, with molecular weight cut-off (MWCO) about 600 Da and permeance around 10-12 L/(m2∙h∙bar), exhibited good dye/salts separation performance. In the filtration of a mixed solution of Congo Red (CR) and calcium chloride (CaCl2), the membrane rejected 98% CR and only had 10% rejection of CaCl2. In addition, this membrane processed an excellent antifouling property. In the BSA fouling test, the pure water flux recovery ratio (FRR) was 99%. It is expected that the PVA/SMA-PES membrane can be used in organic desalination.