Objective：To measure the labeling rate，radiochemical purity，and specific activity of 131I-labeled recombinant human thy－rotropin（rhTSH） as a targeting probe，and to investigate the distribution in vivo and radioimmunoimaging（RII） of 131I-rhTSH in a human differentiated thyroid carcinoma（DTC）-bearing nude mice model. Methods：rhTSH was labeled with 131I by the chloramine T method，and radioactively labeled rhTSH was purified using Sephadex G25M column. The labeling rate，radiochemical purity，room temperature stability，and serum stability were determined using paper chromatography，and the specific activity was calculated. Fur－thermore，the biodistribution and RII of the radioactively labeled drug in the K1 nude mice model were studied. Results：The labeling rate，radiochemical purity，and specific activity of 131I-rhTSH were（93.04±1.13）%，（97.71±1.14）%，and（4.92±0.06） MBq/μg，respectively. The radiochemical purity of 131I-rhTSH placed at room temperature for 1，6，12，and 24 hours was（92.94±0.34）%，（91.81±0.64）%，（91.38±1.20）%，and（90.43±0.74）%，respectively；after incubation with serum for 1，6，12，and 24 hours，the radiochemical purity was（92.59±0.73）%，（91.33±0.98）%，（91.01±0.73）%，and（89.58±1.33）%. Biodistribution and single photon emission computed tomography in the tumor-bearing K1 nude mice model showed that 131I-rhTSH was selectively concentrated in tumor tissues and the target/non-target ratio reached the highest at 24 hours with the clearest tumor imaging. Conclusion：The 131I-rhTSH molecular probe was successfully prepared，which has a good targeting effect in DTC-bearing nude mice model，laying a foundation for further diagnosis and treatment of DTC.