Doped lanthanum chromites show lattice expansion under high temperature reducing atmospheres. We have proposed a numerical simulation model for analyzing the static and the transient expansion behavior of the doped lanthanum chromites under a stationary oxygen potential gradient or a stepwise change of oxygen potential in the atmosphere. A lanthanum chromite interconnector plate, 100 X 100 X 3 mm, was found to warp under a stable solid oxide fuel cell operating condition. The maximum displacement of the center part normal to the originally flat surface was calculated to be about 0.77 mm. A stepwise change of the atmospheric condition caused a transient oxygen potential gradient in a lanthanum chromite rod, 3 x 3 x 20 mm, resulting in a deformation of the sample. The calculated tensile stress coming from the transient deformation was as high as 50 MPa or more.