Provided is a method for determining movements of band gaps of semiconductor nanocrystal quantum dots in different media. A quantum dot model in a medium background is established, a concept of image charges is introduced, the sizes and positions of mirror-image charges are determined, interaction potential energy of electrons, holes and the image charges is added to Hamiltonian of excitons, a Schrodinger equation of the excitons is solved by using a perturbation method to obtain a band-gap energy expression of the quantum dots in the medium background, the band gaps of the quantum dots in the medium background can be obtained by substituting exciton Bohr radiuses of the quantum dots, relative dielectric coefficients, particle sizes, body material band-gap energy, relative dielectric coefficients of the medium background and parameters into the expression, and the band-gap movements of the quantum dots in different background media are determined finally. By adopting the method, band-gap movements of the quantum dots identical in size in different background materials can be specifically calculated, and a direct and powerful tool is provided for design of photoelectronic devices and research on the optical characteristics of semiconductor nanocrystal materials.