Sn1-2xFexNbxO2(0.45≤x≤0.50) samples were prepared at 1000 ℃ via a simple chemical co-precipitation method. The effects of the concentrations of Sn doped on the structures and magnetic properties of the samples have been investigated. A systematic variation from monoclinic to orthorhombic FeNbO4 structure was observed with increasing Sn content. The phase evolutions were observed from monoclinic structure with x=0.50 to the coexistence of monoclinic and orthorhombic structures with x=0.48, 0.47, 0.46, and then to orthorhombic structure with x=0.45. Antiferromagnetic behavior was observed for all the samples, and the magnetic ordering temperatures decrease with increasing Sn concentration, which further indicated the sequence of phase transitions. The results suggest that the incorporation of Sn can stabilize the orthorhombic FeNbO4.