Disclosed is a method for preparing structured graphene on a SiC substrate on the basis of Cl2 reaction, the procedures are as follows: firstly, performing standard cleaning to a SiC sample chip; depositing a layer of SiO2 on the surface of the SiC sample chip and engraving a figure window on the SiO2 layer; then arranging the windowed sample chip in a quartz tube, introducing a mixed gas of Ar and Cl2 into the quartz tube, reacting the bare SiC with Cl2 for 3-8 min at 700-1100° C. to generate a carbon film; arranging the generated carbon film in Ar gas, annealing for 10-30 min at 1000-1200° C. to generate the structured graphene on the window on the carbon film. The method is simple and safe; the generated structured graphene has a smooth surface and low porosity and can be used for making microelectronic devices.