The microstructure and magnetostriction of Fe83Ga17Tby (y=0, 0.2, 0.4, 0.6, 0.8) alloys were investigated. Results show that the cast alloys are mainly composed of A2 phase with a little L12, DO3 and DO19 phase. L12 phase and DO3 increase with the increasing of Tb content in Fe83Ga17Tby alloys; ternary additions of Tb element have conduced to the formation of (200) texture from the binary Fe-Ga alloy; equiaxed grains change into columnar grains and Tb grain boundary enrichment are observed by backscattering electron images and point analysis in the ternary alloys of Tb addition. Magnetostriction is strengthened by accession of Tb. The most felicitous Tb addition is 0.2at%, and Fe83Ga17Tb0.2 can produce magnetostrictive strain of 1.5×10-4 in low field. Spin-orbit coupling is affected by outer shell electron which might result in magnetostriction enhancement