The invention discloses a preparation method of a reverse osmosis membrane modified by an oxidized graphene/polyvinyl alcohol coating. The preparation method comprises the following steps of: preparing a nascent reverse osmosis membrane in advance, then coating polyvinyl-alcohol crosslinking reaction liquid containing oxidized graphene on the nascent reverse osmosis membrane, and finally obtainingthe reverse osmosis membrane modified by the oxidized graphene/polyvinyl alcohol coating. The preparation method disclosed by the invention has the advantages that the oxidized graphene and serine are introduced into the polyvinyl alcohol coating to carry out modification on the polyvinyl alcohol coating, so that the problems of reduction of water flux and easy dropping of the polyvinyl alcohol coating of the reverse osmosis membrane modified by the polyvinyl alcohol coating can be improved.