A method and device for modulating a brightness-grayscale curve of a display device are provided. The method includes determining an applicable standard brightness-grayscale curve for eye perception; obtaining theoretical brightness values corresponding to respective grayscales of the display device based on the applicable standard brightness-grayscale curve for eye perception and at least one of an eye pupil change factor, an environmental factor and a factor related to the display device; modulating brightnesses of the display device according to the theoretical brightness values corresponding to the respective grayscales of the display device. The above method is a solution to the problems of low grayscale details, backlighting, high grayscale saturation, and transition-color unevenness. The problem is solved that a visible grayscale in a dimmed session is no longer distinguishable in a bright environment. And a quantifiable standard for modulation control is provided.