The invention discloses a preparation method of coral reef-shaped indium oxide. The method comprises the following steps: 1) dissolving indium chloride, sodium dodecanesulphonate and urea in ethanol to obtain a mixing solution; 2) heating the mixing solution obtained in the step 1), reacting the mixing solution to generate precipitate; and 3) separating the precipitate obtained in the step 2), washing the precipitate, drying and annealing the material to obtain the coral reef-shaped In2O3. The prepared coral reef-shaped In2O3 has high sensitivity on trace quantity NO2 under low temperature environment, and is the high-performance gas-sensitive material having latent application value.