Ultrafine　WC-Co　materials　were　prepared　by　a　developed　route　combining　in-situ　synthesis　of　composite　powder　and　sinter-HIP　technique.　Simultaneous　enhancement　in　fracture　toughness　and　transverse　rupture　strength　has　been　achieved　in　the　prepared　cemented　carbide.　Based　on　detailed　characterizations　of　Co　binder　phase,　dislocations　in　WC　grains　and　interfacial　features,　the　mechanisms　for　co-enhancement　in　fracture　toughness　and　strength　of　cemented　carbides　are　proposed.