Abstract: Shear thickening fluid was prepared by sonochemical method mixing SiO₂ with different mass fraction and polyethylene glycol（PEG） with different molar mass, and then impregnated into aramid fiber to make STF-aramid composite. The dynamic and static stab resistance and flexibility of the composite were studied and compared with pure aramid fabric. Compared STF of different proportion of SiO₂ to PEG, the results show that with the increase of SiO₂ mass fraction, the force between particles increased, and the friction between particles also increased, so the shear thickening ability of STF was obviously enhanced, and it was more obvious at higher SiO₂ mass fraction. In the static stab resistance test, STF-aramid composite containing PEG with molar mass of 200 g/mol had better stab resistance than PEG with other molar mass under the same mass fraction of SiO₂ particles. In the flexibility test, the bending angle of STF-aramid fiber decreased with the increase of SiO₂ mass fraction and PEG molar mass.