The　fracture　mode　of　an　experimental　Ni-based　single　crystal　superalloy　containing　topologically　close-packed　phases　at　ambient　temperature　was　investigated　by　a　simple　and　practical　testing　method.　Microstructural　investigation　and　compositional　analyses　were　performed　on　the　matching　fracture　surfaces　of　a　small　scale　specimen　after　the　impact　experiment.　It　is　suggested　that　the　weak　TCP/gamma＇　interface　coherency　resulted　in　the　interfacial　decohesion,　which　was　the　main　fracture　mode　for　the　investigated　superalloy　under　the　impact　load　at　ambient　temperature.