Taking the small offices and residences for a studied object, this paper analyzes the process and major factors to affect the concentration and size distribution of indoor inhaled particulate matters, founds the deposition model, the penetration model and the mass balance model to predict the concentration and size distribution of indoor inhaled particulate matter. According to the real-time measuring data, the feature of building defense structure and the concentration and size distribution of outdoor inhaled particulate matters, the deposition ratio, the penetration factor and indoor air capacity are used as the input parameters of the mass balance model. We have put to the proof of the deposition model, the penetration model, simulated the mass balance model, then predicted the concentration and size distribution of indoor inhaled particulate matters.