The geotechnical material’s actual mesostructure is significant in that its characteristics will largely affect its macroscopic mechanical behavior. With the digital image processing technology being more and more mature

the partial differential equations (PDE) method based on variation level set attracts increasing attention meanwhile finds increasingly more application in the field of image processing. C-V model

as a frequently used method

is a typical one among those using the PDE method. This paper deals with how to use C-V model combined with background filling technology to realize the three-phase split (feldspar

quartz and mica) of the granite pictures after the digital image of the rock has been got; thus to provide the conditions for further mechanical analysis. The purpose of quantifying the mesostructure of rock can be achieved by the method described in this paper

which ultimately can be used to get pictures that accurately reflect the internal characteristics of the rock

thus to provide real geometry model for finite element analysis in the future. The numerical value results indicate that the PDE method is very effective indeed. By selecting the appropriate number of iterations

it can get a higher quality of the rock mesostructure quantitative geometric images consistent with the real mesostructure images.