Objective：To observe the effects of chronic particulate matter 2.5（PM2.5） exposure on major organs in Sprague Dawley（SD） rats through establishing long term PM2.5 exposure model of SD rats. Methods：Forty male SD rats（80-94 g，28 days old） were ran－domly assigned to three groups：ten in saline control group，fifteen in low dose group[2 μg/100（g·d）] and fifteen in high dose group[16 μg/100（g·d）]，and instilled with 0.9% saline or PM2.5 respectively every day for sustaining 60 days. At 24 h after the last exposure，the rats were sacrificed and the lungs，heart，liver，spleen and kidney were removed for gross observation and pathological examination. Results：Compared with those of normal group，the weight of PM2.5 exposure group was obviously reduced，especially the appearance of the lungs was significantly changed，the organization structure of lung and heart was damaged with obvious inflammatory reaction. The liver，spleen and kidney also had inflammation. Conclusion：Long exposure of automobile exhaust source PM2.5 can cause inflam－mation lesions in rats’ lung，heart，liver，spleen，kidney，and the damage of lung and heart is much more serious.