Our body motion is adjusted properly under 1G on the earth. Thus changes in gravitational environment have significant impact on our motor control. Further, it may affect on our ability in motor learning and memory. Although some astronauts informally reported difficulties in their body control under microgravity, no quantitative research on this issue has been conducted. Here we performed the prism adaptation of a hand-reaching task under different gravitational environments. We compared learning and forgetting curves, and memory retention rates of the prism adaptation performed in upright vs. supine position under 1G, and those under 1G vs. 2G in upright position. We demonstrate that quicker learning, less forgetting and greater memory retention rates are obtained in supine position and under 2G in comparison with their counter part.