The sub-pixel rendering method includes: obtaining a digital image, in which the digital image includes multiple pixels, each of the pixels includes multiple grey levels, and the number of the grey levels in the digital image is greater than the number of the sub-pixel structures; performing a gamma transformation on each of the grey levels to obtain multiple sub-pixel luminances; performing a sub-pixel rendering algorithm on the sub-pixel luminances to obtain multiple rendered sub-pixel luminances; and transforming the rendered sub-pixel luminances into multiple rendered grey levels, and driving the display panel according to the rendered grey levels, in which the number of the rendered grey levels is equal to the number of the sub-pixel structures.