The invention provides a gamma curve adjusting method and device and a display device. The gamma curve adjusting method comprises the following steps: setting N testing gray scales; adjusting until a corresponding chromaticity coordinate of each testing gray scale is in a corresponding preset chromaticity coordinate range and detecting actually measured brightness corresponding to each testing gray scale; obtaining an actual gamma curve according to the testing gray scales and the actually measured brightness; and when the testing gray scales are greater than or equal to a first preset gray scale or smaller than or equal to a second preset gray scale, adjusting red gamma voltages corresponding to the testing gray scales so that an absolute value of difference between the corresponding actual relative brightness of the testing gray scales and the standard relative brightness of the testing gray scales is smaller than preset brightness difference. By the gamma curve adjusting method and device and the display device in an embodiment of the invention, the gamma curve can be corrected, and requirements of chromaticity coordinates can be met.