The　compatibility　of　polymer　blends　is　pivotal　for　their　performance　enhancement　due　to　the　large　surface　tension　and　weak　interaction　among　individual　components.　In　this　work,　epoxide　hyperbranched　polyurethanes　(EHPU)　was　used　to　realize　the　compatibility　between　silica　(SiO2),　generated　in　situ　from　tetraethoxysilane,　and　benzoxazine　(BZ).　The　compatibilization　effect　and　mechanism　of　EHPU　on　SiO2/BZ　were　investigated　via　the　differences　of　cure　characteristics　and　kinetics　between　BZ,　SiO2/BZ,　and　EHPU-SiO2/BZ　blend.　EHPU-SiO2/BZ　blend　exhibited　lower　initial　curing　temperature　and　wider　curing　window　than　those　of　SiO2/BZ　and　neat　BZ.　In　addition,　the　co-curing　reaction　was　existed　between　EHPU　and　BZ,　which　contributed　to　the　reactive　compatibilization.　More　importantly,　the　growth　of　SiO2　particles　was　hindered　by　the　nonreactive　compatibilization　due　to　the　hydrogen　interaction　between　EHPU　and　the　silanols.　Thus,　the　compatibilization　of　EHPU　on　SiO2/BZ　blend　is　a　result　of　the　synergetic　effect　of　the　hydrogen　interaction　and　the　co-curing.　©　2018　Wiley　Periodicals,　Inc.　J.　Appl.　Polym.　Sci.　2018,　135,　46879.　©　2018　Wiley　Periodicals,　Inc.