Because of the presence of water vapor, YBa₂Cu_3-YAg_yO_7-x degrades easily in the atmosphere and thus very difficult to put it to practical use. When Cu is partially substituted with Ag, however, there is not much a decrease in the critical temperature (T_c):T_c is 89 K compared with 91 K without substitution. Moreover, partial substitution of Ag increases density, hardness, and superconducting particle size and above all improves considerably its stability in water. In this study YBa₂Cu_3-YAg_yO_7-x and YBa₂Cu_3-YAg_yO_7-x as a result of a partial substitution of Ag for Cu were synthesized by pyrophoric method. We investigated their stabilities in water by XRD, SEM, and EPMA after immersing samples in distilled water for 3 hours. We can see that YBa₂Cu_3-YAg_yO_7-x was the largest particle size and anticorrosion behavior.