Objective To investigate the length of hospitalization for patients with papillary thyroid carcinoma undergoing ¹³¹I treatment after bilateral thyroidectomy. Methods A total of 38 patients with papillary thyroid carcinoma who underwent ¹³¹I treatment after bilateral thyroidectomy were selected and divided into the low-dose treatment group (n=25, therapeutic dose=3.7 GBq) and high-dose treatment group (n=13, therapeutic dose>3.7 GBq). The radioactive exposure doses of all patients at 48 h and 72 h after ¹³¹I administration and reference source (0.37 GBq) were measured at a distance of 1 m. Results The difference of radioactive exposure doses of two groups at 48 h after ¹³¹I administration was statistically significant (t=2.244, P=0.039). The radioactive exposure doses of all patients at 72 h after ¹³¹I administration were lower than that of reference source. The radioactive exposure doses of 9 patients (3 from low-dose group and 6 from high-dose group) at 48 h after ¹³¹I administration were higher than those of reference source and the difference of two groups was statistically significant (χ²=5.520, P=0.040). The radioactive exposure doses after ¹³¹I administration did not correlate with age and levels of Tg, TgAb, and TSH in serum. Conclusion The radioactive exposure doses of patients with papillary thyroid carcinoma at 72 h after ¹³¹I treatment decrease rapidly and are significantly lower than the national criterion of 0.37 GBq, so patients can be discharged from hospital and perform self-isolation. The radioactive exposure doses of patients at 48 h after high dose ¹³¹I treatment are relatively high.