Provided are an organic semiconductor film and a preparation method thereof. The preparation method includes at least the following steps: preparing an inorganic nanocrystal with a shell structure, performing synchronous ion exchange on an anion and a metal ion in the inorganic nanocrystal with the shell structure to obtain a modified inorganic nanocrystal with a shell structure and a relatively stable structure, dispersing the modified inorganic nanocrystal with the shell structure and a conjugated organic small molecule in an organic solvent to obtain a dispersion, and forming the dispersion into the organic semiconductor film.