A novel kind of impact protective material, named as impact protective micro-gel (IPM), was synthesized via a precipitation copolymerization of a compound containing boron and silanol. Diphenylmethane diisocyanate (MDI) was introduced as the chain extender to enhance its impact protective performance. Its rheological properties and morphology were investigated. Three-dimensional (3D) spacer warp-knitted fabrics were dip-coated with the IPM made with and without use of MDI, and the impact protective performance of 3D finished fabrics was assessed by drop impact tests. The results show that the adjustment of the MDI content can adjust the real cross-linking density of the IPM due to the entanglement of polymer chains, and an appropriate cross-linking density can endow dilatant properties to the IPM samples. The results also show that the impact protective performance of 3D spacer fabrics finished with the IPM can be significantly improved. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2345–2351, 2013