The purpose of this experiment was to examine trend of F, Zn, Sr and tannic acid on subsurface and the state of the surface of galss ionomer cement (GIC) containing 10% HY-agent (HY10) after immersion in distilled water for three months. To determine the amount of each element at the layers of the subsurface of GIC, using a Microkator, the layers of known thickness were serially removed by abrasion with a lapping film. Electron microprobe elemental analysis (EPMA) of F, Zn and Sr were also made in the X-ray concentration map. Furthermore, the surface of GIC discs was examined by scanning electron photomicrography(SEM). The F content decreased more and at a deeper region than those of Zn, Sr and tannic acid in the analysis of these elements on the subsurface of GIC discs. The analysis by EPMA showed the same tendency as that of their contents, and F and Sr accumulated together. In SEM the surface of the samples after immersion became rough with some deposit .On the other hand, the surface of the samples before immersion was smooth.Furthermore, the condition of roughness on the surface of HY10 was more severe than that of HY0 (control) . These findings suggested that F was released more easily from a deeper portion of the GIC discs than the others.