Provided is a KAI1 protein controlling the cell cycle of a hematopoietic stem cell and a use thereof, and more specifically, a composition including a KAI1(CD82) polypeptide or a gene encoding the same for controlling the cell cycle of a hematopoietic stem cell, or a pharmaceutical composition for preventing or treating blood tumors. Further provided, KAI1(CD82) is expressed only in a hematopoietic stem cell (LT-HSC) which is the uppermost stem cell in the hierarchy of the hematopoietic stem cell, can obtain an LT-HSC with high purity using the KAI1, and thus can inhibit various side effects of hematopoietic stem cell transplantation by transplanting only an LT-HSC with high purity. In addition, KAI1 importantly acts on the quiescence of an LT-HSC, and has resistance against cell damage due to various stresses (5-FU, irradiation, etc.) by maintaining the quiescence of the LT-HSC. Thus, it is expected that the cell can be used for making a cell bank and can be used as a blood tumor cell therapy product through cell transplantation.
