The Ruddlesden-Popper type Pr2-xNiO4±delta is one of the most potential membrane materials for the design of intermediate temperature solid oxide fuel cell cathodes and oxygen separation membranes due to their extremely high oxygen diffusivity. A-site deficiency improves the oxygen diffusivity in the Pr2-xNiO4±delta, which may be caused by a lower diffusion barrier for oxygen atoms at the A-site. The composition of Pr2-xNiO4±delta (x=0.0, 0.5, 1.0, 1.5, 2.0) at maximum oxygen mobility is known only roughly until now, and the oxygen diffusion mechanism of this material is also not clear. In this work, nuclear density maps based on neutron diffraction will be created at for different A-site deficiencies, the oxygen sites will be determined based on Rietveld refinement.