Nd-Fe-B permanent magnets have been used in many industries like hard disk, electric vehicle and wind power for its excellent comprehensive magnetic properties [1-2].The Nd2Fe14B-based magnets with heavy rare earth elements such as Dy, Tb have much better temperature stability, higher energy product and coercivity [3].For the balanced utilization of rare earth elements without sacrifice magnetic properties and decreasing the usage of heavy rare earth elements to reduce the cost, better understanding the mechanism of the Nd-Fe-B permanent magnets with heavy rare earth elements, the investigation on the phase relations and phase diagrams of Fe-RE systems are needed.In this work, the Fe-RE (RE=Gd, Dy, Tb) binary systems were assessed using the CALPHAD method based on the reported experimental phase equilibria data and thermodynamic data [4].As a result, a set of thermodynamic properties and phase equilibria conforming data were obtained.Although the phase relations and phase diagrams of Fe-RE systems are basically corresponds, more experimental data are still needed.