In order to achieve high-fidelity representation of colors, it needs to do some purposeful interference when colors are conversed, so the color gamut mapping which is the main technology to ensure visual matching would be used during this process. And the accurate visualization of out-of-gamut between images and devices plays an important role in color gamut mapping, so a method of the 3D visualization of out-of-gamut in graphic communication based on segment maxima algorithm was proposed in this paper. And this method mainly had two steps, the first step was that the device color gamut boundary points could be obtained when used the color conversed information in digital output device profile, so as to generate accurate device color gamut. The next step was that out-of-gamut points could be obtained through making comparison between device gamut and digital image gamut, as result that the area of out-of-gamut could be presented in digital images and image gamut according to the out-of-gamut cloud dots. The advantages of this method were that it can encourage us to predict whether the image gamut is beyond the output device gamut in advance, and then it can help us to select appropriate color gamut mapping algorithm according to the result of out-of-gamut judgment, so as to realize the accurate reproduction of colors.