To investigate influence of Ca doping on oxygen permeation properties in orthorhombic perovskite (Sm, Ca)FeO3 series, we investigated the oxygen permeation flux (J(O2) ), electrical conductivity and crystal structure of Sm1-xCaxFeO3 (x = 0.5). Then we compared the investigated results with those of the other compositions: x = 0.2, 0.25 and 0.3. The Joy increased and the activation energy E-J of Joy decreased with increases of the Ca content from x = 0.2 to 0.5. The Sm1-xCaxFeO3 (x = 0.2-0.5) showed no remarkable difference in total electrical conductivity at temperatures higher than 800 degrees C, meaning that no significant influence of the electrical conductivity on the Joy. The lattice distortion relating to the FeO6 tilt relaxed with the Ca doping. The bottleneck size for ion migration decreased with the Ca doping. The results suggest the relaxation of lattice distortion is a main factor to make ion migration easier and then improve the J(O2).