This study focuses on the fact that adsorbing moisture from the air is enhanced with oscillating flow induced by acoustic wave, which mechanism has not been clear yet. The objective is to investigate the mass transfer to adsorbent with oscillating flow by CFD. A pack of granular silica gel was modeled in CFD scheme. The air flow is assumed to be the sum of background uniform flow and oscillation flow. The CFD analysis predicted the behavior of adsorption over time with various velocity amplitude. With uniform flow, only the front particles of upstream side adsorb moisture. In contrast, the particles facing to the downstream side also adsorb moisture when oscillating flow exists. The results indicate that the oscillating flow going back and forth induces the enhancement to provide moisture from the downstream side to adsorbent particles.