Silica-Magnesium　Potassium　Phosphate　cement　mortar　(MSPM)　which　is　made　up　of　dead　burnt　magnesia　powder,　Dipotassium　phosphate　K2HPO4　center　dot　3H(2)O　(P),　silica　fume　and　a　certain　proportion　of　ISO　standard　sand,　is　used　as　repairing　materials　helping　study　the　bonding　performance　between　MSPM　and　ordinary　Portland　cement　mortar　(OPM).　In　this　research,　the　effect　of　polyvinyl　alcohol　powder　on　MSPM　bonding　strength　(flexural　bonding　strength　and　flexural　two-sided　bonding　strength)　was　investigated.　The　bonding　mechanism　was　studied　with　X-ray　diffraction　(XRD),　Mercury　intrusion　porosimetry　(MIP)　and　environmental　scanning　electron　microscopy　(ESEM).　The　experimental　results　show　that　PVA　powder　has　good　film　forming　properties.　The　PVA　film　formed　by　PVA　powder　will　encapsulate　reactants　(silica　fume,　magnesium　oxide)　and　hydration　products　(struvite-K)　in　MSPM　system,　and　form　structuring　O-Mg-O　with　Mg2+.　In　addition,　the　PVA　film　encapsulates　the　surface　of　Ca(OH)(2)　and　ettringite　crystals　at　the　interface,　and　complexes　with　Ca2+　to　form　O-Ca-O　molecular　chain　structure,　reducing　the　number　of　crystals　at　the　interface.　When　the　PVA　content　reaches　0.4%,　the　bonding　performance　between　the　OPM　and　the　MSPM　is　greatly　improved　due　to　the　good　bonding　properties　of　the　PVA　film　and　the　ionic　complexation　reaction　occurring　at　the　bonding　interface.　However,　when　the　content　of　PVA　reaches　0.6%,　PVA　cannot　be　uniformly　dispersed　in　the　reaction　system　due　to　agglomeration.　In　addition,　the　covering　effect　of　PVA　film　has　affected　the　normal　progress　of　hydration　reaction,　so　the　improvement　in　bonding　performance　at　the　bonding　interface　is　limited.　(C)　2019　Elsevier　Ltd.　All　rights　reserved.