The invention discloses a preparation method of a quantum dot sensitized solar cell graphene composite counter electrode, and belongs to the technical field of quantum dot sensitized solar cell counter electrode synthesis. According to the technical field, the preparation method comprises the following steps: preparing polysulfide electrolyte; preparing graphene oxide solution; polishing a copper sheet with sand paper, bathing the copper sheet in hydrochloric acid solution at 70 DEG C for 17-20min, taking the copper sheet out, and cleaning the copper sheet with de-ionized water; putting the copper sheet in the graphene oxide solution for 5-12h hydrothermal reaction at 90-120 DEG C, and freezing and drying a prepared graphene composite copper sheet; and vulcanizing the graphene composite copper sheet in the polysulfide electrolyte for 10min, and finally, getting a quantum dot sensitized solar cell graphene composite counter electrode. The preparation method is simple and of high repetition rate. Prepared graphene can be uniformly and tightly grown on a metal sheet. By using the quantum dot sensitized solar cell graphene composite counter electrode in quantum dot sensitized solar cells, the stability of cells can be improved effectively.