The invention discloses an adaptive readable image enhancement method under sun based on an image content. The method comprises the following steps of step1, image input: converting image data of an RGB space of an ith frame of input image into data which contains and is not limited in an YCbCr space and acquiring a brightness value Y; and step2, image chroma space conversion: converting the image data from one color space into other color spaces and the like. In the invention, under the sun, a readable effect is improved obviously and the method is suitable for a chip design.