Summary: In the present study (3‐methacryloxypropyl)trimethoxysilane (MPMS) containing acrylic resin/alumina hybrid materials with various alumina contents were prepared. The effects of ethylacetoacetate (EAA) content, catalyst type, and water content during sol–gel process for alumina sols on the microstructure and properties of the hybrid materials were investigated by SAXS, AFM, DSC, TGA, and nano‐indentation tester, respectively. It was found that the hybrid materials exhibited a homogeneity and the alumina phase of the hybrids had mass fractal dimension and open structure. The thermal and mechanical properties of the hybrid materials were obviously improved when alumina was incorporated. The EAA contents, catalyst type, and water content during sol–gel process for alumina sols had obvious effects on the microstructure and properties of the hybrid materials.