Optical glass, a preparation method thereof, a backlight module and a display module. The optical glass comprises a glass substrate and optical masterbatches, which are dispersed in the glass substrate, each optical masterbatch comprises a quantum dot fluorescent agent inner core and an encapsulation shell which encloses the quantum dot fluorescent agent inner core. A quantum dot fluorescent agent is protected by the encapsulation shell and the luminous efficiency is high; when the optical glass is applied to a display module, the color gamut may be improved; moreover, the glass is capable of preventing against the invasion of water vapor, even the quantum dot fluorescent agent at an edge of the glass rarely fails, and an edge failure size is basically avoided; meanwhile, the expansion coefficient is small, and an expansion space reserved during assembly is extremely small.