Abstract: According to the failure problem of the solid rocket engine insulation material caused by deformation incompatibility between the reinforced fabric and rubber matrix under impact loading, the polyimide fiber weft knitted fabric reinforced nitrile rubber (NBR) composites were designed and prepared. Based on the rib structure, two kinds of fiber fineness, three kinds of loop length and two lay-up structures were selected. The effects of reinforced structure on the low velocity impact properties of composites were investigated. Results show that the composites with large tow fiber, long loop length and orthogonal lay-up have higher peak load and absorbed energy. Profilometer and microscope observation were adapted to observe the damage modes of impacted composites. The specimens are not penetrated under 20.1 J impact loading. It is found that matrix cracking along the fiber direction and plastic deformation along the thickness direction are the main damage mode of composites.