The invention discloses a bromide perovskite quantum dot material with high brightness and good monochromaticity and a preparation method thereof; the quantum dot material is a CH3NH3PbBr3 quantum dot material having the light emitting half-peak width of 15-20 nm and the quantum yield of 50-70%. The preparation method comprises the following steps: (1) using bromide ions for replacing chlorine ions in CH3NH3Cl, carrying out a reaction with PbCl2 to generate CH3NH3PbBr3, and preparing a CH3NH3PbBr3 precursor solution; and (2) converting the precursor solution into toluene, and forming the quantum dot material. Flammable and explosive methylamine is not required, the dangerousness is low, a series of complex and time-consuming processes for preparing CH3NH3Br are omitted, the stability of the precursor solution is good and can be used repeatedly, and thus the method is a method suitable for industrial production.