The invention discloses a palladium nano particle-modifying indium oxide nanosheet composite material as well as a preparation method and application thereof. Indium nitrate, resorcinol, N,N-dimethylformamide and acetone are used as raw materials to prepare an indium-series organic framework nanosheet of a three-dimensional net structure by utilizing a high-temperature high-pressure method, thenthe palladium ion-modifying indium-series organic framework nanosheet of the three-dimensional net structure is prepared by virtue of an electrostatic absorption process, and finally the nano particle-modifying indium oxide nanosheet composite material is prepared by virtue of air calcining and reductive gas reduction. The palladium nano particle-modifying indium oxide nanosheet composite materialnot only has high specific surface area and good gas sensitive characteristic, but also can be used as a sensing layer of a resistance-type metal oxide gas sensor to realize the ultra-sensitive and high-selective detection for carbon disulfide gas, and moreover, no expensive detection equipment is needed, the detection cost is low, the operation is simple, the detection time is short, and rapidness and high efficiency can be realized.