  In this article, we studied the role of oxygen in Pr$_{2}$CuO$_{4\pm\delta}$
thin films fabricated by polymer assisted deposition method. The
magnetoresistance and Hall resistivity of Pr$_{2}$CuO$_{4\pm\delta}$ samples
were systematically investigated. It is found that with decreasing the oxygen
content, the low-temperature Hall coefficient ($R_H$) and magnetoresistance
change from negative to positive, similar to those with the increase of
Ce-doped concentration in R$_{2-x}$Ce$_{x}$CuO$_{4}$ (R= La, Nd, Pr, Sm, Eu).
In addition, $T_c$ versus $R_H$ for both Pr$_{1-x}$LaCe$_{x}$CuO$_{4}$ and
Pr$_{2}$CuO$_{4\pm\delta}$ samples can coincide with each other. We conclude
that the doped electrons induced by the oxygen removal are responsible for the
superconductivity of $T^\prime$-phase parent compounds.
