In order to develop a safe and effective gene therapy carrier, some toxicological and biodynamical ex- periments were carried out on silica nanoparticles (SiNPs). First we prepared SiNPs with appropriate portions of cyclo- hexane, deionized water and ethyl silicate, and then trans- fected the modified SiNPs and GFP plasmid DNA complex into the HT1080 cells to test the effectiveness of transfection for gene therapy. At the same time, we injected the SiNPs into a number of mice through tail vein. Then we made the mice crossed to evaluate the acute, long-term and reproduc- tive toxicity. In vivo distribution analysis and pathological examination were made on both adult mice and their off- spring. SiNPs were uniform and had an average diameter of 40 nm, and the modified SiNPs carried exogenous DNA molecules into target cells and the transferred GFP fusion gene was effectively expressed in the cells. The SiNPs injected via tail vein were widely distributed in almost all of tissues, and the injected mice had the ability to reproduce normally. The in vivo and in vitro results of this study clearly show that SiNPs can be used as a safe and effective carrier for gene transfection and gene therapy. In order to develop a safe and effective gene therapy carrier, some toxicological and biodynamical ex-periments were carried out on silica nanoparticles (SiNPs). First we prepared SiNPs with appropriate portions of cyclo-hexane, deionized water and ethyl silicate, and then trans - fected the modified SiNPs and GFP plasmid DNA complex into the HT1080 cells to test the effectiveness of transfection for gene therapy. At the same time, we injected the SiNPs into a number of mice through the tail vein. Then we made the mice crossed to evaluate the acute, long-term and reproduc-tive toxicity. In vivo distribution analysis and pathological examination were made on both adult mice and their off-spring. SiNPs were uniform and had an average diameter of 40 nm, and the modified SiNPs carried exogenous DNA molecules into target cells and the transferred GFP fusion gene was effectively expressed in the cells. The SiNPs injected via tail vein were widely distributed in almost all of tissues, and the injected mice had the ability to reproduce normally. The in vivo and in vitro results of this study clearly show that SiNPs can be used as a safe and effective carrier for gene transfection and gene therapy.