The invention relates to a flexible conductive thin film compositing a two-dimensional graphene and a one-dimensional nanowire and a preparation method of the flexible conductive thin film. The preparation method includes the following steps: dispersing the graphene, the nanowire and dispersion auxiliary in solvent, obtaining graphene/nanowire solvent which is well dispersed after the solvent is processed through ultrasound concussion, and obtaining a graphene/nanowire composite thin film after the graphene/nanowire solvent is processed through vacuum filtration and drying. The thickness of the composite thin film is 10 nanometers to 1000 micrometers, the composite thin film has good strength and flexibility, square resistance is between 0.001 ohm per square and 3000 ohms per square, and electrical conductivity is between 0.01 siemens per centimeter to 5000 siemens per centimeter. The graphene/nanowire composite thin film which is obtained with the adoption of the preparation method has good strength, flexibility, and electrical conductivity, and is controllable in thickness, cuttable in shape, simple in preparing process, easy to operate, low in manufacturing cost, and suitable for solar batteries, energy storage, heat dissipation, catalysis, sensing, and conductive composite material fields.