Magnesium　potassium　phosphate　cement　(MKPC)　produced　by　dead　burnt　magnesia　(MgO)　and　potassium　dihydrogen　phosphate　(KH2PO4)　is　a　rapid　repairing　material.　In　order　to　repair　concrete　structures　under　dry-wet　cycles　and　sulfate　attack　condition,　the　degradation　of　MKPC　under　the　dry-wet　cycles　in　5　wt%　Na2SO4　solution　was　analyzed　by　investigating　the　mass　loss　and　compressive　strength　in　this　paper.　In　addition,　the　influences　of　fly　ash　and　quartz　sand　on　the　MKPC　were　also　discussed.　The　degradation　mechanism　of　the　MKPC　samples　and　influence　mechanism　of　fly　ash　and　quartz　sand　were　analyzed　based　on　the　pore　structure,　XRD　and　SEM.　The　mass　and　compressive　strength　of　MKPC　progressively　decrease　after　dry-wet　cycles.　The　pore　structure　of　MKPC　was　optimized　by　fly　ash;　the　sample　with　fly　ash　showed　improved　durability　under　dry-wet　cycles.　The　sample　with　quartz　sand　showed　poor　durability　under　dry-wet　cycles　since　the　quartz　sand　led　to　the　initial　defect　and　interfacial　transition　zone　in　the　MKPC　matrix.　(C)　2019　Elsevier　Ltd.　All　rights　reserved.