The invention discloses a method for preparing graphene oxide from walnut shells serving as a carbon source. The method mainly comprises steps as follows: 1) pretreatment of the walnut shells; 2) carbonization treatment; 3) catalytic graphitization; 4) acidification and stripping. The problems that the production cost is high, preparation is limited by carbon sources and the size of obtained graphene oxide is relatively small in graphene oxide preparation process in the prior art are solved, and the method has the characteristics that the raw materials are widely sourced, the production cost is low, the repeatability is good and the product quality is high and has broad application prospects.