In this paper, the as-cast alloys (Fe₈₁Ga₁₉)_1-xB_x (x=0,0.06,0.1,0.15,0.20) were prepared by vacuum melting method. The microstructure, morphology and composition of the alloys were characterized by X-ray diffraction, scanning electron microscopy, energy dispersion spectrum and metallography. The magnetostrictive properties of the alloys were measured by resistance strain gauge method.The results show that due to the addition of trace element B, the magnetostrictive properties of the alloy are improved, and the maximum saturation magnetostrictive value λs=138ppm is reached at x=0.10.The results show that the structure of (Fe₈₁Ga₁₉)_1-xB_x alloy is mainly α-Fe body center cube.The addition of B element causes lattice distortion and improves the magnetostrictive properties of the alloy, and the other part is distributed in the form of B-rich precipitates inside the grain.After the addition of element B, the grains of the alloy change into large columnar crystals, which are favorable to the magnetostrictive properties of the alloy. Because of the small grain boundaries, the large columnar crystals reduce the factors hindering the magnetic domain movement, which is favorable to the magnetostrictive properties of the alloy.