The invention discloses a double-gate graphene transistor with aluminum oxide as gate dielectric and a manufacturing method thereof. The double-gate graphene transistor with the aluminum oxide as the gate dielectric mainly solves the problems of reduction of carrier mobility and carrier scattering in a graphene channel due to top grate dielectric of a graphene transistor in the manufacturing process in the prior art. The double-gate graphene transistor is structurally characterized in that two gate electrodes are arranged on the two sides of the graphene channel respectively to form a double-gate structure. The manufacturing method includes the first step of depositing a layer of aluminum oxide on the surface of a washed silicon carbide sample wafer and etching out a structural graph on the aluminum oxide layer, the second step of placing the etched sample wafer into a quartz tube, feeding carbon tetrachloride to react with silicon carbide to generate a carbon film, then placing the sample wafer into argon to carry out annealing to generate graphene and carrying out etching on the portions, 60-400 nanometers away from the two sides of the graphene channel, of the aluminum oxide layer to form gate grooves, and the third step of depositing metal on the sample wafer and etching the sample wafer to form a metal contact layer of the transistor. The double-gate graphene transistor manufactured through the method is capable of effectively improving the carrier mobility ratio and the modulation capacity of the gate electrodes on the channel current.