Abstract: <SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: "Times New Roman"; mso-bidi-font-size: 12.0pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体">Surface modification process on industrial grade magnesium hydroxide [Mg(OH) <SUB>2</SUB>] using 4 types of silane coupling agents with same hydrophilic groups was carried in aqueous solution at room temperature,then the surface modified Mg(OH)<SUB>2</SUB> was mixed in melting state with polypropylene (PP) at the filling level of 35%.Surface modification results were evaluated by the means of FT-IR and SEM.Influences of different silane coupling agents on flame retardant performances and mechanical properties of MH/PP material were mainly investigated.Results indicated that silane coupling agents could increase dispersion and compatibility of Mg(OH)<SUB> 2</SUB> in PP and improve mechanics property of Mg(OH)<SUB>2 </SUB>PP,but had low effect on its flame retardant properties;dodecyltrimethoxysilane had better stability in aqueous phase and can preferably co-ver Mg(OH)<SUB>2</SUB> surface.Cantilever notch impact strength increased by 50% and elongation at break enhanced six times after the material modified by dodecyltrimethoxysilane and thus good modification effect had been reached.</SPAN>