Traditional　magnesium　phosphate　cement　(MPC)　has　problems　such　as　high　carbon　emissions　and　uncoordinated　development　of　setting　time　and　strength.　For　the　purpose　of　reducing　the　carbon　emission　of　MPC,　improve　its　strength　and　promote　the　comprehensive　utilization　of　brucite　resources,　magnesium　phosphate　cement　(NBMPC)　was　prepared　by　using　natural　brucite　(NB)　as　magnesia　material,　and　modified　by　ultrafine　metakaolin　(UMK).　The　results　showed　that　the　initial　setting　time　of　NBMPC　without　UMK　was　30　min,　the　compressive　strength　of　3　h　and　28　d　was　5.17　MPa　and　46.57　MPa,　respectively.　When　UMK　content　was　10　%,　the　maximum　initial　setting　time　of　NBMPC　was　51　min.　When　UMK　content　was　30　%,　the　highest　compressive　strength　of　NBMPC　at　3　h　and　28　d　was　35.56　MPa　and　70.74　MPa,　respectively.　The　products　of　NBMPC　were　MgNH4PO4.6　H2O,　hydrated　MgHPO4　and　a　small　amount　of　calcium　phosphate　compounds.　The　modification　mechanism　of　UMK　on　NBMPC　was　chemical　modification　and　physical　filling.　On　the　one　hand,　the　chemical　environment　of　Si　and　Al　in　UMK　changed　in　NBMPC,　resulting　in　the　formation　of　aluminosilicate　phosphate,　MgNH4PO4.6　H2O　containing　Al　and　Si,　and　calcium　phosphate　compounds　containing　Al　and　Si.　Amorphous　AlPO4　was　formed　in　NBMPC　with　higher　UMK　content.　UMK　promoted　the　early　crystallization　of　MgNH4PO4.6　H2O,　reduced　the　production　of　MgHPO4.7　H2O　and　inhibited　its　transformation.　Moreover,　UMK　improved　the　pore　size　distribution　of　NBMPC　and　reduced　its　porosity.　When　preparing　NBMPC,　the　content　of　UMK　can　be　optimized　according　to　the　engineering　type　and　construction　environment.