The present disclosure provides a display device and a control method thereof. The control method of the display device comprises: obtaining, based on the first light output ratio and the second light output ratio, a first luminous flux set composed of values of luminous fluxes output by a combination path at a current bit depth, and a second luminous flux set composed of values of luminous fluxes output by the combination path at a target bit depth respectively; obtaining, based on the first luminous flux set and the second luminous flux set, a value of a luminous flux to be expanded to achieve the target bit depth at the current bit depth; and adjusting a mapping relationship between the value of each luminous flux to be expanded and a value of a maximum luminous flux in the first luminous flux set corresponding to the current bit depth based on a display bit depth of the display device.