Abstract: Because of many unique advantages in sewage treatment and seawater desalination, nanofiltration (NF) membrane has been the focus in membrane research. Graphene oxide (GO) can be used in the preparation of composite nanofiltration membrane due to its special molecular structure and surface charge property. In this article,improved Hummers method is used to prepare graphene oxide with high oxidation level, then pressure assisted self-assembly technique is used to prepare GO-PVDF composite NF membrane. The influence of GO-PVDF composite membrane on the rejection and flux is investigated through the removal test to NaCl and Na₂SO₄ by varying defferent factors including loading of GO and concentration of salt solution. The experimental results show that increasing the capacity of GO contributes to better desalination effect. Under the same condition, the rejection efficiency of GO membrane to Na₂SO₄ is better than that to NaCl, and higher removing rate is observed in lower salt-concentration solution. Through the stability evalution of NF membrane by long duration test, it can be concluded that the flux and rejection of GO-PVDF composite membrane are stable and the rejection rate of NaCl and Na₂SO₄ can reach 58.9% and 76.6% respectively after 12 h.