In this article, we studied the role of oxygen in Pr2CuO 4±δ thin films fabricated by polymer assisted deposition method. The magnetoresistance and Hall resistivity of Pr2CuO 4±δ samples were systematically investigated. It is found that with decreasing the oxygen content, the low-temperature Hall coefficient (RH ) and magnetoresistance change from negative to positive, similar to those with the increase of Ce-doped concentration in R2−xCexCuO4 (R= La, Nd, Pr, Sm, Eu). In addition, Tc versus RH for both Pr2−xCexCuO4 and Pr2CuO 4±δ samples can coincide with each other. We conclude that the doped electrons induced by the oxygen removal are responsible for the superconductivity of T -phase parent compounds. PACS numbers: 74.72.Ek, 81.15.-z, 73.50.-h, * kuijin@iphy.ac.cn 1 P. A. Lee, N. Nagaosa, and X. G. Wen, Rev. Mod. Phys. 78, 17 (2006).