The target of this study is to figure out how dose sandtray-therapy can improve the elementary senior year girls’ ego-identity. The sandtray-therapy was progressed once a week, 50 minute for each time, 20 times for total, from October 19th year 2011 to February 29th year 2012. The study analyzed the Korean ego-identity examination by measuring it both in beforehand and after the fact. The subordinate scopes for Korean ego-identity examination are concluding independence, proprioceptive, goal directedness, initiative, closeness. Also, the study was analyzed with having awareness of the positive element and negative element that can appear in the progress of sandtray-therapy, and divided the development step that appeared in sand tray treatment from interviewed children into Kalff’s the development steps, which are animals and plants step for first, struggle step for second, and adaptation step for third. As the result of sandtray-therapy, it shows positive changes to creating ego-identity for girls. After the treatment, the study figured out that all the factors in subordinate scopes are improved except for proprioceptive. Moreover, as the sandtray-therapy is in progress, the positive changes are appeared. As time goes on, the negative factors were remarkably decreased, while the positive factors were increasing. This change happens because the sandtray-therapy gives children, not only the experience for curing psychologically, but also strengthen inner power for enduring various stress and problem that can easily face in normal life. Therefore, suppressed and inherent emotion can be expressed by sand tray, the safe and appropriate way and can also make children to understand and integrate themselves. Thus, this study identified sand tray treatment is helpful for improving elementary senior girls’ ego-identity.