The invention relates to black mesoporous SnO2 nanosheets enriched in oxygen vacancies and a preparation method of the nanosheets. The method specially comprises the following steps: (1) preparing a SnS2 nanosheet precursor by adopting a chemical vapor deposition process; (2) placing the SnS2 nanosheet precursor in an atmosphere furnace, and performing calcination in an oxidizing atmosphere to obtain ordinary white mesoporous SnO2 nanosheets; and (3) placing the white mesoporous SnO2 nanosheets in an atmosphere furnace, and performing annealing in a mixed atmosphere of argon and hydrogen to obtain the black mesoporous SnO2 nanosheets rich in oxygen vacancies. The method provided by the invention has the advantages of a simple preparation process, low costs, and no pollution, and the finally obtained sample is a nanosheet having a mesoporous structure, and has a large specific surface area, excellent electrical properties, and obvious absorption effect on visible light; and the sample obtained by the method can be widely used in the fields of gas sensing, catalysis, solar cells, lithium ion batteries and the like.