The invention relates to an ethyl acetate gas sensor using Al-doped cubic-structure In2O3 microparticles as a sensitive layer and a preparation method thereof, belonging to the technical field of gas sensors. The sensor is sequentially composed of an Al2O3 substrate, a Pd metal interdigital electrode and an Al-doped cubic-structure In2O3 microparticle sensitive layer from bottom to top, wherein the sensitive layer is prepared on the Pd-metal-interdigital-electrode-bearing Al2O3 substrate by an application technique; and the particle size of the Al-doped cubic-structure In2O3 microparticles is 1-1.2 mu m. The Al doped into the cubic-structure In2O3 microparticles causes lattice defects, and the lattice defects are beneficial to enhancing the gas-sensitive response of the gas-sensitive material. The technique is simple; and the prepared ethyl acetate gas sensor is small in size and suitable for mass production, and thus, has important application value. The preparation method is simple, has the characteristics of low cost and high response restoration speed, is hopeful to implement large-scale production, and has favorable detection performance for ethyl acetate gas.