Objective: To observe effects of Yuzhang Decoction on in vitro proliferation of bone marrow CD_(34) cells in the patient of aplastic anemia (CAA) and its mechanism. Methods: To adopt monoclone antibody-immune magnetic beads separation system (MACS) to separate and purify CD_(34) cells in bone marrow of the patient of CAA, and make cell culture, applying ~3H-TdR incorporation to detect effect of Yuzhang Decoction on proliferation of CD_(34) cells of bone marrow. Results: CD_(34) cells of bone marrow showed concentration-dependent proliferation in the Yuzhang Decoction group with significantly differences (P