As　a　type　of　excellent　rapid　protective　material　with　fast　hardening　and　high　early　strength　characteristics,　magnesium　phosphate　cement　(MPC)　is　used　as　the　cementitious　material　to　fabricate　concrete　canvas.　For　a　thick　MPC　canvas,　sufficient　hydration　reaction　is　crucial　in　keeping　its　integrity.　Borax　is　used　to　adjust　the　hydration　progress　of　MPC　in　warp-knitted　fabrics.　The　effects　of　different　borax　contents　(0　%,　1　%,　2　%,　3　%,　4　%,　5　%,　6　%)　on　the　compactness　of　reaction　products　and　the　mechanical　properties　of　MPC　canvas　are　evaluated.　In　addition,　SEM,　XRD,　hydration　heat,　and　X-CT　are　used　to　systematically　analyze　the　hydration　morphology,　products,　exothermic　process,　and　pore　structure　of　MPC　canvas.　The　results　show　that　borax　can　effectively　delay　the　setting　time　of　MPC,　addressing　the　issue　of　incomplete　hydration　of　MPC　powder　in　thick　canvas.　The　4　%　borax　content　(B4　sample)　can　ensure　the　complete　reaction　in　a　20　mm　thick　MPC　canvas,　achieving　the　maximum　compressive　and　flexural　strengths　of　26.37　MPa　and　4.9　MPa　at　7　d,　respectively.　Borax　effectively　optimizes　the　pore　structure　of　MPC　canvas　and　achieves　a　dense　bond　at　the　interface　between　MPC　and　the　canvas　fabric　with　the　minimum　porosity　of　11　%　in　the　B4　sample.　Therefore,　borax　is　crucial　for　the　structural　of　MPC　canvas.