The invention relates to field of video treatment, and provides a method and device for optimizing an image, wherein the method and device provided by the invention are used for solving the problem of severe display color distortion at the high contrast region in the prior art, wherein the method comprises: acquiring sampling values a, b, c and d of input video Cb or Cr signal positions; acquiring the maximum value and the minimum value from the sampling values of positions a, b, c and d; calculating the Cb or Cr signal value o:o= lambda max*max (a, b, c, d)+lambda min *min (a, b, c, d) aftersampling, wherein lambda max+lambda min=1; and outputting the Cb or Cr signal value o. According to the embodiment of the invention, the color distortion can be reduced maximally at the high contrastregion of color signals, such as characters in a webpage.