Three hundred and twenty one-day-old healthy Arbor Acres(AA) broilers were randomly divided into two groups,i.e.,experimental group and control group,and later bred in the chicken houses of different sanitary environmental management conditions.To better understand the impacts of different raising environments on broilers’ immune function,the concentrations of aerobic bacteria,fungi,and endotoxins in the air of the chickens’ houses were determined periodically.Meanwhile,newcastle disease antibody(ND-Ab) levels and immune organ indexes of broilers were detected.The results showed that the microbial concentrations of the experimental group were significantly higher than those of the control group (P＜0.05).Newcastle antibody levels of the control group were higher than those of the experimental group significantly (P＜0.05) at 35,42 and 49 days.The spleen index was influenced significantly (P＜0.05) compared with the control one and very significant impact on the thymus (P＜0.01) was identified,while little effect on the bursa (P＞0.05) was observed.Therefore,the poor sanitary condition and high concentration of microbial aerosols may have a bad effect on the immune functions of broilers,from which it could be concluded that keeping good sanitary condition of raising environments is one of the important measures to keep animals healthy.