Abstract: In this paper, by adding EVA to magnesian oxychloride cement in different amount and adopting different EVA for the fiber treatment, mechanical and microscopic tests for the composites samples were carried out to research the effect of EVA emulsoid on the interfacial adhesion strength and discuss its mechanism. The results indicate that EVA added to cement as an additive can improve the interfacial adhesion strength of the glass fiber reinforced magnesian oxychloride cement obviously; while using EVA as a surface active agent to deal with glass fibers has no evident influence on the interfacial adhesion strength of composites.