Herein we propose control of polymerization kinetics to prevent inherent scattering problem of holographic photopolymer system that is caused by a phase separation between matrix and photopolymerized grating polymers. To elucidate this, in this letter, phase stability of the photopolymer system was studied with molecular dynamic simulation of Flory-Huggins theory and was investigated in the respect of polymerization kinetics. It was controlled with the variables of monomer conversion and degree of polymerization by varying both reaction time and rates. In addition, volume grating fixing effect of post ultraviolet treatment on photopolymer was examined. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3562032]