Objective To understand the radiation dose changes of patients receiving iodine after operation for differentiated thyroid cancer,and to discuss the best protection when patients were discharged and during the process of staying in hospital.Methods A total of 74 patients with differentiated thyroid cancer who received ¹³¹I treatment after surgery were selected. At 24 h,48 h,72 h and 96 h after treatment,the radiation dose levels on the neck and 1m far away from the patients were measured by the radionuclide therapy monitoring robot,and compared with the reference standards of discharge. Results At 24 h,48 h,72 h and 96 h after ¹³¹I treatment,the radiation dose 1m away from the patient was 270.11（202.46,427.18）,64.02（39.01,101.19）,16.74（10.07,27.69）,5.28（3.41,10.40）respectively. At 24 h,48 h,72 h and 96 h after ¹³¹I treatment,0 patient,2 patients（2.7%）,52 patients（70.3%）and 70 patients（94.6%）met the discharge dose requirements. Conclusion Radiation dose changes of thyroid cancer patients after ¹³¹I treatment is great among different patients. It is suggested to dynamically detect the radiation dose at 1 m after ¹³¹I treatment and individualized discharge schedule is advocated. Medical staff should be well protected when contacting patients,and the radionuclide therapy monitoring robot can be used to complete part of the work.