The　electrochemical　properties　of　Nd2Fe14B　single　crystal　grain,　conventional　sintered　NdFeB　and　SPS　NdFeB　in　electrolyte　were　studied.　The　microstructures　and　compositions　of　the　magnets　were　investigated　with　scanning　electron　microscope　(SEM)　and　energy　dispersive　X-ray　detector　(EDX).　Polarization　curves　in　3.5%　NaCl　solution　show　that　Nd2Fe14B　single　crystal　grain　has　displayed　most　positive　corrosion　potential　and　the　SPS　NdFeB　magnet　has　more　noble　potentials　compared　with　the　conventional　sintered　one.　Compared　with　conventional　sintered　NdFeB　magnet,　SPS　processed　magnet　has　original　microstructure　i.e.　the　grain　size　of　the　Nd2Fe14B　main　phase　is　fine　and　uniform,　and　the　fine　Nd-rich　phase　does　not　form　along　the　grain　boundaries　of　main　phase,　but　agglomerates　into　the　triple　junctions.　The　pathways　for　corrosion　propagation　are　restricted　and　the　inter-granular　corrosion　process　though　Nd-rich　phase　in　the　magnet　is　suppressed　effectively.　Therefore,　the　SPS　NdFeB　magnet　possesses　excellent　corrosion　resistance.　Autoclaves　test　indicates　that　a　strong　correlation　has　been　established　between　an　increase　in　the　total　rare　earth　level,　which　corresponds　to　the　amount　of　Nd-rich　phase,　and　an　increase　in　the　corrosion　rate.　The　results　show　that　chemical　character;　microstructure　and　the　amount　of　Nd-rich　phase　determine　the　corrosion　resistance　of　magnets　and　indicate　an　intergranular　corrosion　leads　to　poor　corrosion　resistance.