The invention provides an InP quantum dot and a preparation method therefor. The InP quantum dot comprises an InP core modified with a metal salt and a shell wrapping the core, wherein the shell is ZnSe/ZnS or ZnSexS(1-x), x is greater than 0 and is not greater than 1, the half-peak breadth of the InP quantum dot is less than or equal to 50nm, and the quantum efficiency is more than or equal to 70%. Due to the modification of the metal salt, dangling bonds on the surface of InP are eliminated, the loss of energy in form of non-optical properties can be reduced, and the fluorescent quantum yield of quantum dots with metal salt modified InP is increased; in addition, the difference of lattice constants of InP and ZnSe is relatively small, so that the shell with S and Se can relatively easily coat the surface of the InP core, and then, the InP quantum dot provided by the invention has relatively high quantum efficiency and stability; and meanwhile, the half-peak breadth of the InP quantum dot is less than or equal to 50nm, so that the particle size of the quantum dots is relatively uniform.