The precipitation behaviors of fine MnS and other second phase particles in hot band, decarburized sheet and 875 oC annealed sheet before secondary recrystallization of conventional grain oriented electrical steel were investigated. It is indicated that the small particles as inhibitors would dissolve in the matrix during cold rolling, and precipitate again in following annealing treatment. The particles inside grains would keep retarding the grain boundary migration. It was found that the particle densities in all grains were quite different before initiation of secondary recrystallization and might be grain orientation dependent, in which Goss grains showed higher particle density. It is expected that the grain boundaries would move towards the grains with lower particle density more easily and promote the rapid growth of Goss grains. The reason for difference of particle densities in different grains is quite complicated. The influence of possible different dislocation densities and the different precipitation behaviors of second phase particles are mentioned.