Abstract: Objective To label the anti-β-human chorionic gonadotropin monoclonal antibody with β. Methods It was direct labeled using SnCl₂ as a reduction agent. Results The labeling procedure was finished within 1.5 hours. The labeling efficiency of the labeled anti-β-human chofionic gonadotropin monoclonal antibody was 88.1%-97.5%, _99mTc colloidal was 0.96%-1.27%, _99mTcO₄^- was 1.1%-9.92%. And it retained its specific biological activation. Conclusion This direct method is simple, rapid and stable, and it hope to be used as radioimmunodiagnosis for gestational trophoblastic turnout.