The invention belongs to the field of gas-sensitive material preparation, and especially relates to a metal oxide / polyaniline composite resistor-type gas-sensitive element and a preparation method thereof. According to the invention, a metal oxide porous nano-grade solid is grinded; deionized water is added and a slurry is prepared; the slurry is coated on a substrate; high-temperature sintering is carried out, and a porous thick film is formed; doped polyaniline is grinded and is prepared into a slurry with an added solvent; the slurry is coated on the porous thick film; the material is naturally dried in the air, such that a gas-sensitive material composite coating is formed, and the gas-sensitive element is prepared. According to the metal oxide / polyaniline composite resistor-type gas-sensitive element provided by the invention, the adhesiveness between the porous thick film and the substrate, and between the porous thick film and polyaniline is good, and falling is prevented. The gas-sensitive element has the advantages of good selectivity, high sensitivity, short response time, short recovery time, good recovery performance, low cost, and simple preparation method. Especially, the gas-sensitive element is used for detecting low-concentration nitrogen oxide gas.