Since indoor particles accumulate on the floors easily, there is a high possibility of allergic reactions in child whose breathing zone is near the floor surface. Ventilation is one of the best ways to remove indoor particles. The aim of this study is to clarify the diffusion characteristics of indoor particles in different ventilation strategies room by experiments and CFD. Comparison of the number of particle in experimental monitoring point shows that the number of particle in the ceiling exhaust was a little higher than the slit exhaust ventilation strategy. CFD simulations concerning diffusion fields completed. From the data we can conclude that slit exhaust ventilation strategy will produce less indoor particles in the room to compare ceiling exhaust ventilation strategy.