A　series　of　Ni-P　alloys　(Ni-rich)　have　been　synthesized　and　solidified.　It　is　found　that　the　solidification　microstructure　of　the　Ni-19.0　at.%P　alloy　that　has　long　been　regarded　as　the　eutectic　composition　contains　many　primary　phase　dendrites　besides　rod　eutectics.　In　contrast,　only　rod　eutectic　microstructure　appears　in　the　samples　of　Ni-19.6　at.%P,　and　this　alloy　shows　the　lowest　end　temperature　of　melting　among　all　the　compositions　investigated.　The　results　indicate　that　the　actual　eutectic　composition　at　the　Ni-rich　part　of　the　Ni-P　system　is　Ni-19.6　at.%P.　The　eutectic　temperature　is　determined　to　be　about　1163　K　by　the　differential　scanning　calorimetry　analysis.