The purpose of this study was to determine the effective preparation of a bone marrow graft by centrifugation. The experimental 4 groups were divided into Group A(5min/400G), group B(7min/400G), group C(10min/400G), and Group D(5min/600G) after aspiration of 12 case bone marrows. The results were as follows: Group A and Group B were not effective preparations of a bone marrow graft as seen in the total cell count and the viable cell count. Group C was the most effective preparation of a bone marrow graft among 4 groups. Group D had a the less viable cell count than Group C but the viable cell count was enough to record.