This paper is to explore the different anti oxidant and inflammation effects of short time high dose and long time low dose fine particular matter (PM2.5) on rats. Forty eight healthy male C57BL/6 rats were randomly divided into six groups, eight in each. Low dose group, moderate dose group and high dose group were exposed to PM2.5at 100 μg·m-3, 150 μg·m-3 and 250 μg·m-3 on average, respectively, using the artificial climate environment expose cabinet. 〖JP2〗Meanwhile, three blank 〖JP〗groups were also set. After exposure, C reactive protein (CRP), constructivenitric oxide synthase (cNOS), homocysteine (HCY), interleukin8 (IL 8) were analyzed. The results showed that the levels of CRP, HCY and IL 8 in long term low dose group are significantly higher than those in the short term 〖JP2〗highdose group (P<0.05, P<0.01). 〖JP〗The inhibition level of cNOS in the lowdose group is also significantly higher than that in the short term highdose group (P<0.05, P<0.01). The ranking of PM2.5 exposure to health damage effect is low dose 72 h, moderate dose 48 h and high dose 28.8 h when the PM2.5 exposure dose is same.