The calcareous soil is a special rock and soil medium which composes more than 50 % Ca CO3. It has irregular grain shape

which correlates mechanical and engineering properties of compression and filling in calcareous soil. Using optical microscope

the grain projection of calcareous soil is got. With image processing tool of matlab

grain shape of calcareous soil is analysed in two ways:one is the traditional statistics way; the other is the fractal geometry. The results show that the grain shape of calcareous soil can be expressed by fractal dimension. And the character is getting more obvious when the grain is getting smaller. And the character of calcareous soil is analysed with its special cause of formation.