The samples of Pr1.85Ce0.15CuO4-x and Pr2CuO4-x were prepared by a solid reaction method. X-ray diffraction patterns reveal that single-phase Pr1.85Ce0.15CuO4-x and Pr2CuO4-x have been obtained with a small amount of impurity phases. For the samples of Pr1.85Ce0.15CuO4-x, superconductivity transitions are observed in the range of 0.05≤x≤0.20, and Tconset is 24.5 K. The samples of Pr2CuO4-x can not achieve superconductivity only by adjusting the oxygen content. By the comparison of different effects of the oxygen content on structure and magnetic properties, it is found that in Pr1.85Ce0.15CuO4-x samples the reason of superconductivity realization by adjusting oxygen content is free carrier introduction, while for Pr2CuO4-x the reason why the superconductivity does not realize is that oxygen vacancies do not appear in the same oxygen position. The relative mechanism was discussed