Abstract: This paper pretreated the SEM imagines of gypsum board and gypsum particleboard to improve the imagine quality so that the microstructure of the material was further understood. The techniques of digital imagine processing, such as edge detection and imagine segmentation were used to partially or totally treat the SEM imagines of gypsum particleboard. The imagine informations including the shape , size, area and lager distribution of the gypsum crystal were obtained. The lager distribution and the distribution of the gypsum crystal on the wood particleboard surface were primarily estimated. Good improvement was made as well.