To evaluate the design of environment safeguard and management effect of ward, the samples of three wards in Chongqing hospital were taken and the concentration of air bacterial aerosol and distribution characteristics in wards were known by bacterial culture, finding that all wards have bacterial contamination to some extent. Air bacterial aerosol concentration is positively correlated with people density and temperature, negatively correlated with humidity, little to do with the unit type. Ward air bacteria aerosol concentration in summer is higher than in winter, especially in paediatric ward, which may reach 2865 cfu·m^-3.The size distribution of bacterial aerosol has close relation with season, the high percentage of airborne bacteria concentration is centered on stageⅠto stage Ⅲ in winter and stage Ⅲ to stageⅤin summer. The median diameter of airborne bacterial in winter is bigger than summer and both of them is smaller than 4.7 μm.