Objective: to study the toxicity of SiO2 nanoparticles to the organs in vivo after intratracheal instillation,and provide the basis for safety evaluation of SiO2 nanoparticles.Methods: 40 six to eight weeks of BALB/c female mice were randomly divided into control group(saline),low dose group(7 mg/kg bw),middle dose group(21 mg/kg bw),and high dose group(35 mg/kg bw).1 day and 15 days after five times of non exposed intratracheal instillation infected(once every three days),the mice were sacrificed and the right kidneys,livers,hearts and spleens were collected and embedded in paraffin.The morphology of hematoxylin-eosin(HE)staining tissue sections were observed under light microscopy after.Results: compared with control group,there were alveolar interval thickening,inflammatory cells infiltration,and a small amount of small arterial thrombosis in the lungs; granulomatous inflammatory cell infiltration and a small amount of focal necrosis of liver cells in the livers; red pulp enlargement,hyperemia,and more visible scattered megakaryocytes in the spleens,in the SiO2 nanoparticles treated groups in a dose-dependent manner.After 15 days of the injection,the damages alleviated as time pass by.Conclusion: the intratracheal instillation of SiO2 nanoparticles will influence the major organs in the mice and mainly displays in the inflammation and injuries in the lung,liver and spleen.