Abstract: Objective: To evaluate the safety of Nano silica on the tissues of the mice, the mice were taken oral administration with the food grade silica Nanoparticles ( Nano silicon dioxide, Nano-SiO₂) , after 12 weeks the content of silica in serum, livers, kidneys and testis of silica were detected, and the livers and kidneys of mice were observed.Methods: Male KM mice were randomly divided into different groups including the control group ( 0.05% BSA) , Nano-SiO₂groups ( 100, 500, 1000 mg/kg/day) and micron-SiO₂group ( 1000 mg/kg/day) . 84 days later, all animals were killed and the tissues were collected. The histopathological changes of livers, kidneys, testis and other tissues of the mice by HE staining were obversed.Content of silicon in livers, kidneys, testis and serum were detected by ICP-OES. The content of alanine aminotransferase ( ALT) , aspartate aminotransferase ( AST) and blood urea nitrogen ( BUN) in serum were measured by colorimetric method.Results: All the results were compared with the control group. The HE staining showed the varying differences of pathological changes in the livers, kidneys and testicular tissue abnormalities and the high dose of Nano-SiO₂ group was the most.With the increase of Nano-SiO₂ doses, the contents of ALT, AST and BUN were increased.The examination of the silicon in the livers, kidneys, testis and serum of the Nano groups were inhibited in dose-dependent manner.Compared with the same dose of micron group, the above results of the Nano group were more serious. Conclusion: Taking orally with food grade Nanosilicon for a long time, the poison mayaccumulate in the body's liver, kidney, testis and other tissues, leading to different histopathological damages and affect their functions.