The oblate spherical powder with micro-pores(MOSP)can change the transfer mode of heat and quantity in the process of its combustion, reduce its web thickness and increase its burning surface, so as to achieve the rapid combustion of propellant in weapons. In view of the causes of the hole formation in MOSP, several factors of hole formation were discussed: air, solvent vapor and water. By means of eliminating or weakening the factor of hole formation by water, standing for removing the air bubbles and quick heating respectively, determining bulk density and observing section microstructure of MOSP with a microscope, the mechanisms of hole formation by air and by solvent vapor were confirmed. Results indicate that the air is a tiny factor of hole formation, and can be ignored. The range of pore diameter is from micro/nano to several millimeters, and the pores randomly distribute in MOSP. The solvent vapor is not a factor of hole formation, and the quick heating can not make pores in MOSP, but it can change the bulk density of MOSP along radial.