Abstract: Objective To explore the methods for labeling CDTPA-coupled CD45 monoclonal antibody (mAb) with yttrium-90 (90Y) for potential acute myeloid therapy. Methods CD45 mAb was labeled with 90Y by CDTPA and the labeling rate, radiochemical purity, final specific activity, and immunological activity of the mAb were detected. Results With the optimal molar ratio of CDTPA/Ab at 20∶1, the labeling rate was 95%, radiochemical purity 99.8%, and final specific activity 1.9 mCi/mg. This conjugate was stable in vitro with comparable immunological activity in comparison with unlabeled CD45 mAb. Conclusion 90Y-CDTPA-CD45 mAb possesses good properties as an ideal targerting therapeutic agent for acute leukemia.