In order to research the image enhancement method based on RGB model and the objective evaluation based on the full reference image，based on the relevance theory of color components obtained after decomposing color image based on RGB model，we applying the gray transform theory of gray image processing based on pixe1 processing. The enhancement algorithms are proposed based on the same transformation coefficients of the pixelvalue range and the same proportional scale of transformation coefficient. The experimental results show that the algorithms can be used to enhance the image based on RGB model. The calculated data from a group of formula ofthe objective quality assessment based on the error of the unit pixel also can be used to the objective quality assessment of color image. It is consistent with the results of subjective quality assessment after enhancing the color image. So it can be used for the quality evaluation of color image enhancement.