Abstract: To investigate the formation mechanism of internal stress of the polymer bonded solid particulate from the viewpoint of the mesoscopic mechanics, a SEM equipped with a tensile apparatus was used to study the damage in microstructure of the materials. By SEM, it was seen that the original damage of material affects the tensile destruction greatly; at the tensile break, materials produce the fracture around the crystal and the fracture through the crystal at the same time, the bond produces large tensile change. The results indicate that bond and particulate match well; the material has fracture toughness. Polymer bonded solid particulate is a viscoelastic material related to original damage.