Phase relations for Fe-Ti-Zr ternary system at 1023K have been investigated by means of diffusion triple together with electron probe microanalysis technique, a series of tie-lines and tie-triangles have been determined and the isothermal section at 1023K has been established, and seven three-phase fields have been figured out. It was found that all of the Fe-Zr and Fe-Ti binary phases show large ternary solubility, and Zr and Ti can substitute for each other to a certain degree. The largest solid solubility of Ti in Fe2Zr and in FeZr3 is about 8.5 at.% Ti and 35.7 at.% Ti, and of Zr in Fe2Ti and FeTi is about 5.6 at.% Zr and 6.3 at.% Zr, respectively. The solubility range of Fe2Ti, FeTi, Fe2Zr and FeZr3 is 64.9 72.7 at.% Fe, 46.6-49.1 at.% Fe, 65.8-71.7 at.% Fe and 20.9-24.3 at.% Fe, respectively. No ternary compound was found.