The impregnation of flexible fabric with shear thickening fluid (STF) is a potential method for surface modification of bullet-proof fabrics, which can significantly increase the pullout force and pullout energy of yarns, thereby increasing the impact resistance of flexible fabrics. In this work, the STF-impregnated Kevlar 49 plain fabric with SiO₂ as the disperse phase and ethylene glycol (EG) as the dispersant is prepared. The yarn pullout tests are performed on the neat fabric and the STF-impregnated fabric respectively, showing that the load-displacement curves of the neat fabric and the STF-impregnated fabric present similar tendency and can be divided into two stages of static friction and dynamic friction. Unlike the neat fabric, the ultimate pullout load of the STF-impregnated fabric occurs in the dynamic friction stage and is significantly larger than that of the neat fabric. In addition, the pullout energy and the in-plane shear deformation of the STF-impregnated fabric are significantly improved, which are related to the mass fraction of STF and the yarn pullout rates.