Abstract: Diatomite often appears white, yellow, black or other colors. The white diatomite is more special, and its strength decreases significantly when it meets water. In order to accurately grasp the engineering characteristics of white diatomite, it is necessary to master the microstructure of white diatomite. This paper takes the white diatomite as the research object. We use the SEM test and display the pore characteristics of the white diatomite by numerical method. The overall morphology of the white diatomite is analyzed from the microscopic point of view. At the same time, we quantitatively analyzes the microstructure of the white diatomite, and studies the micro characteristics of the pores of the white diatomite through the binarization analysis and fractal dimension analysis. The results show the following findings. (1)The white diatomite has a unique disordered porous structure. The aggregation of particles is mainly in the form of accumulation polymerization. Its overall structure is mainly in the form of dispersion structure. The contact form is mainly face-to-face. (2)The micro pore size of white diatomite is generally small. The pore size presents an irregular distribution with strong randomness. The pore structure has irregular shape, showing a small pore shape. (3)White diatomite has relatively high surface porosity. It is manifested as small pore size, large quantity and complex structure on the microscopic level. (4)White diatomite has good fractal characteristics. The fractal dimension of diatomite shows a nonlinear decreasing trend under different thresholds. The larger the threshold is, the larger the fractal dimension decreases. At the same time, the fractal dimension value of white diatomite is large. This result indicates that there are more pore structure units on the micro surface of white diatomite, which shows the characteristics of small pores and large number of pores on the macro level.