In order to achieve more accurate image color mapping to the printer color gamut, a new color gamut boundary description method in Lab space is proposed based on region segmentation method. Firstly, in the Lab space, the color gamut boundary description (GBD) is used to describe the color gamut of the printer. Then the printer linear gamut boundary (LGB) is calculated according to the image of each pixel of the hue angle. Finally, the relationship between the L value of each pixel of the image and the L interval of LGB matrix is compared to make sure whether the pixel dot is within the printer gamut boundaries. After dividing the gamut boundary of the printer in GBD, according to the image of each pixel, the printer’s LGB boundary is determined. Therefore the color gamut boundary description method is more accurate. Simulation results show this method could achieve more accurate and intuitive color map image to the printer color.