The　mechanical　properties　and　fracture　toughness　of　magnesium　phosphate　cement　(MPC)　were　studied　in　this　paper.　The　results　show　that　the　strengths　(compressive,　flexural,　axial　tensile　and　splitting　strengths)　of　MPC　increased　rapidly　over　curing　ages　and　then　increasing　rates　slowed　down.　The　compressive　strength　increased　with　the　addition　of　fly　ash,　while　the　tensile　strength　decreased.　For　both　the　specimens　with　and　without　the　addition　of　fly　ash,　the　axial　tensile　strength　was　lower　than　the　splitting　strength.　The　axial　tensile　strength　of　MPC　without　fly　ash　was　1/13-1/10　of　compressive　strength　and　the　axial　tensile　strength　of　MPC　with　fly　ash　is　1/17-1/14　of　compressive　strength.　The　ratio　decreased　over　time.　The　load-deflection　curve　showed　the　failure　mode　of　MPC　is　brittle　failure.　The　fracture　energy　increased　over　time,　while　the　value　was　relatively　small.　The　failure　load　and　the　corresponding　mid-span　deflection　of　MPC　decreased　in　presence　of　fly　ash,　which　results　in　the　further　decrease　of　fracture　energy　of　MPC.　(C)　2015　Elsevier　Ltd.　All　rights　reserved.