Tests and study were carried out on indoor air bacteria pollution in dwelling house inChongqing city. Based on the data of measured bacteria concentration of the indoor air,the reasons for indoor air pollution were analyzed. Ith was found that the bacteria seriously polluted the indoor air. The main factors influencing the indoor air bacteria pollution are moisture, natural ventilation and lighting conditions. The construction forms and decoration of the dwelling house are the secondary reasons for indoor air bacteria pollution. Measures and suggestions of preventing the indoor air bacteria pollution and improving the indoor air quality and environmental quality were presented.