Graphene　nanoplatelets　(GNPs)　are　commonly　regarded　as　an　ideal　reinforcement　for　metal　matrix　composites　because　of　their　excellent　mechanical　properties.　However,　these　excellent　properties　cannot　be　fully　exploited　due　to　GNPs　aggregation　and　poor　bonding　interface.　In　the　present　investigation,　GNPs　with　different　residual　oxygen　amount　were　prepared　by　adjusting　the　amount　of　KMnO4　oxidant　using　the　modified　Hummers　method　as　well　as　thermal　reduction.　The　GNPs-reinforced　ZK60　matrix　composites　(GNPs/ZK60)　were　prepared　through　stir　casting.　Structure　characterization　indicates　there　are　C-O,　C-O-C　and　C-C--O　oxygen-containing　functional　groups　on　the　synthesized　GNPs,　among　which　all　C-C--O　and　parts　of　C-O　groups　are　broken　and　react　with　Mg　to　form　MgO　particles.　The　formed　interfaces　in　terms　of　MgO　in　the　GNPs/ZK60　composites　are　MgO/Mg,　having　a　semi-coherent　interface　structure,　and　MgO/GNPs,　having　an　incoherent　interface　structure.　The　sandwich　interface　structure　of　Mg/MgO/GNPs　improves　the　interface　bonding,　in　which　the　ultimate　tensile　strength　and　elongation　of　the　0.05　wt.%GNPs-4/ZK60　composite　reached　261　MPa　and　12.1%,　increasing　37.4%　and　128.3%,　respectively,　compared　with　those　of　the　monolithic　matrix.　It　is　suggested　the　present　work　might　offer　a　design　guideline　for　graphene　reinforced　metal　matrix　composites.