The invention discloses an indium sulfide photocatalyst with sulfur vacancies. The indium sulfide photocatalyst has a molecular formula of In2S3, abd is used for high-efficiency solar nitrogen fixation. A preparation method of the catalyst comprises the following steps: 1, taking an organic liquid as a solvent; 2, adding an organic substance and an indium salt compound to the organic solvent; 3, filling a reaction kettle with the obtained solution, and performing a constant temperature reaction; 4, cooling the obtained solution to room temperature, centrifuging the cooled solution, respectively washing the obtained reaction product with the organic solvent and an ethanol solution, drying the washed reaction product, and collecting the obtained powder to obtain MIL-68(In); 5, adding an organic sulfide to an organic alcohol solvent, and performing mixing and sufficient stirring; 6, adding MIL-68 (In), and performing mixing and sufficient stirring; 7, filling the reaction kettle with theobtained mixture, and carrying out a constant temperature reaction; 8, cooling the obtained solution to room temperature, centrifuging the cooled solution, washing the obtained solid with water and the ethanol solution respectively, drying the washed solid, and collecting the obtained powder to obtain indium sulfide; and 9, annealing the indium sulfide in a nitrogen atmosphere to produce sulfur vacancies. The catalyst obtained by the method of the invention has the advantages of environmental protection, harmlessness, realization of batch production, and efficient solar nitrogen fixation performance.