The present invention relates to a composition capable of improving storage stability of stem cells. More specifically, the present invention relates to a composition which contains a serum or a plasma for improving cold storage stability of stem cells. The composition for improving storage stability of stem cells according to the present invention can maintain a survival rate of over 90% for at least 9 days without changes in the properties, the number or the size of the stem cells, and thus is useful in the long-term transport of stem cells for cell therapy and the preparation of cell therapeutics injection products having an excellent effect.