La_0.9M_0.1NbO_4-d (M=Sm, Gd, Yb) were prepared via a solid reaction route and single phase was attained by calcining constituent oxides at 1200 ˚C for 5 h. Their phase crystal structure, microstructure and conductivity were investigated. The total conductivity of LaNbO₄ was improved by Sm, Gd, Yb doping, which was mainly attributed to the introduction of oxygen vacancy, and followed the order as La_0.9Sm_0.1NbO_4-d > La_0.9Gd_0.1NbO_4-d >_{La0.9Yb0.1NbO4-d, as shown in the figure acttached}. The highest conductivity (1.76×10^-4 S cm^-1) was achieved for La_0.9Sm_0.1NbO_4-d at 800 ˚C in wet air, more one order higher than that of LaNbO₄.