To　study　the　relationship　between　the　mechanical　properties　of　sintered　NdFeB　magnets　and　composition　of　the　Nd-rich　phase,　sintered　NdFeB　magnets　with　different　mechanical　properties　and　composition　of　Nd-rich　phases　were　prepared　by　spark　plasma　sintering　technology　(SPS).　Several　correlations　including　the　bending　strength　of　the　magnet　to　sintering　temperature　(sigma(bb)-t),　the　rare　earth　content　in　the　Nd-rich　phase　to　the　sintering　temperature　(n(RE)-t)　and　the　iron　content　in　the　Nd-rich　phase　to　the　sintering　temperature　(n(Fe)-t)　were　investigated.　Several　empirical　formulas　for　these　relationships　ware　obtained　by　fitting　these　experimental　curves.　It　is　found　that　there　is　almost　no　change　in　the　sum　of　Re　and　Fe　content,　revealing　that　the　diffusion　direction　of　RE　and　Fe　atoms　in　the　boundary　phase　between　the　main　phases　during　sintering　is　opposite,　and　the　relationship　of　sigma(bb)　to　n(RE)　are　approximately　linear.　Based　on　these,　the　mechanism　of　improving　the　mechanical　properties　of　sintered　NdFeB　materials　via　changing　the　composition　of　Nd-rich　phase　was　discussed.