Cross-linking　with　large　flexible　molecules　is　a　common　method　to　improve　the　stability　and　control　the　interlayer　spacing　of　graphene　oxide　(GO)　membranes,　but　it　still　suffers　from　the　limitation　of　low　water　flux.　Herein,　a　novel　high　flux　GO　membrane　was　fabricated　using　a　pressure-assisted　filtration　method,　which　involved　a　synergistic　chemical　cross-linking　of　divalent　magnesium　ions　and　1,6-hexanediamine　(HDA)　on　a　polyethersulfone　(PES)　support.　The　membrane　cross-linked　with　magnesium　ions　and　HDA　(GO(HDA-Mg2+))　exhibited　a　high　water　flux　up　to　144　L　m(-2)　h(-1)　bar(-1),　about　7　times　more　than　that　of　cross-linked　GO　membranes　without　adding　magnesium　ions　(GO(HDA)),　while　keeping　excellent　rejection　performance.　The　GO(HDA-Mg2+)　membrane　also　showed　an　outstanding　stability　in　water　for　a　long　time.　The　effects　of　magnesium　ions　on　the　GO(HDA-Mg2+)　membrane　were　analyzed　using　several　characterization　methods,　including　Fourier　transform　infrared　spectroscopy　(FT-IR),　scanning　electron　microscopy　(SEM),　X-ray　photoelectron　spectroscopy　(XPS)　and　X-ray　diffraction　(XRD).　The　results　indicated　that　magnesium　ions　not　only　promoted　reasonable　cross-linking,　but　also　improved　the　stacking　of　GO　sheets　to　give　lower　mass　transfer　resistance　channels　for　water　transport　in　the　membranes,　resulting　in　the　ultrahigh　permeance　of　the　GO　membranes.