Current study was conducted to investigate the toxicity of fumed silica, Aerosil 200 nano particles (99.8% Sio2) against adults and larvae of three stored grain insects. Khapra beetle, Trogoderma granarium, drugstore beetle, Stegobium paniceum and red flour beetle, Tribolium castaneum, residual toxicity, seeds germination % and seeds components % for 6 months storage. Results showed that @ highest conc. 1.5 and 2 gm/kg fumed silica was sufficient to cause 100% mortality with T. granarium and S. paniceum after 5 and 2 days of treatment while for T. casteneum which known by its highly resistance for most alternatives, 4 gm/kg recorded 83% mortality after 21 days from treatments. Fumed silica @ lower limit Lc₉₀ can protect wheat seeds from insect infestation until the 4^th month storage. The crude protein %, total carbohydrate%, crude fiber% and total ash% were increased while crude fat % and moisture % decreased in treated grains when compared with untreated grains. Germination % of seeds stored for 6 months after treatment with lower limit LC₉₀ of fumed silica slightly affected comparing with untreated seed. Also chlorophyll analysis showed that fumed silica slightly decreased chlorophyll % in treated seeds. Nano particles by transmission Electron Microscope (TEM) indicates that the original morphology of particles approximately spherical with the diameter varying between 5 to 20 nm.