Ca0.01La0.99−xSmxNbO4−δ (x=0, 0.1, 0.2, 0.4, 0.6, 0.8, 0.99) is prepared by using a solid reaction route, and single phase is achieved. Structural and phase transformation of Ca0.01La0.99−xSmxNbO4−δ have been characterized by high temperature X-ray diffraction. The lattice parameters a, b, c decrease and γ increases with increasing x, at both room and high temperature. The phase transformation temperature increases linearly with increasing x for Ca0.01La0.99−xSmxNbO4−δ. The electrical conductivity of Ca0.01La0.99−xSmxNbO4−δ is measured in wet air. A clear relationship between the structural, phase transformation and electrical conductivity of Ca0.01La0.99−xSmxNbO4−δ is built, which will provide a guideline to tailor the electrical conductivity.