Abstract: As a novel activator in the process of angiogenesis, CD93 may be an important molecular target for tumor surveillance, therefore, ¹²⁵I-anti-CD93 mAb was prepared to study the biological distribution and the characteristics of phosphor screen imaging of ¹²⁵I-anti-CD93 mAb in tumor-bearing mice, to explore its targeting to A549 lung cancer and the feasibility of CD93 positive tumor monitoring. Radionuclide markers ¹²⁵I-anti-CD93 mAb and ¹²⁵I-IgG were prepared and identified; A549 lung cancer bearing mice model was established. ¹²⁵I-labeled anti-CD93 monoclonal antibody was injected into tail vein, and ¹²⁵I-IgG was used as control. Biological distribution and phosphorus screen autoradiography were performed at different time after injection; HE staining and CD93 immunohistochemical staining were performed on tumor tissues. Quantitative data （x +s） were statistically processed by statistical software, and t-test was used for data between groups, P<0.05 was considered statistically significant.The results showed that the labeling rate, specific activity and radiochemical purity of ¹²⁵I-anti-CD93 mAb and ¹²⁵I-IgG were 91.37% and 90.24%, 1 096.44 MBq/mg and 1 082.88 MBq/mg, 96.49% and 94.82% respectively, and the stability of the two markers was still above 90% after 72 hours, there was no statistical difference between the two（normal saline group P=0.93, t=0.09, serum group P=0.13, t=1.90）. Biological distribution of the tumor-bearing mice showed that ¹²⁵I-anti-CD93 mAb were mainly metabolized through the liver and kidney, the tumor tissue (6.42±0.71)%ID/g and the T/NT (tumor/contralateral muscle) uptake ratio was 4.45±0.86 at 48 hours after injection, significantly higher than the control group ¹²⁵I-IgG group (2.45±0.33/1.71±0.24), P<0.05, t=3.07 and P<0.01, t=5.10. The results of dynamic whole body phosphorus screen autoradiography showed that the contours of two groups was clear at 24 hours, and the most clear tumor imaging of the experimental group was obtained at 48 hours after the injection, the tumor radioactivity uptake ratio (tumor area/oppositearea) was 3.34 ± 0.18, significantly higher than that of the control group (1.62±0.19), P<0.01, t=6.52. Immunohistochemical staining showed that the tumor was highly expressed CD93. ¹²⁵I-anti-CD93 mAb is easy to prepare and has good targeting effect on A549 lung cancer tissue. There CD93 may be a new molecular probe for CD93 positive tumor monitoring.