Objective: The aim of this study was to compare the effect of 131I therapy of different clinical stages in postoperative patients with papillary thyroid carcinoma (PTC). Methods: Eighty-seven PTC patients after surgery ablated with high doses of 131I from 2004 to 2010 were retrospectively reviewed. The efficacy of 131I therapy was assessed by three diagnostics that serum thyroglobulin (Tg) was normal or significantly reduced, 131I whole body scan (131I-WBS) was negative or the metastases shrank or the number of them decreased and new metastases was not found in cervical ultrasound examination. The χ2 test was used to analyze 3 factors which might affect the therapeutic efficacy of 131I in patients of different clinical period, including different surgical ways (total or subtotal thyroidectomy along with half or double sides neck lymph node dissection), age (< 45 years and ≥ 45 years) and ablative 131I dose. Results: Of 87 patients, the effective rate of 46 patients I stage was 89.13% (41); the effective rate of 22 cases III stage was 77.27% (17); the effective rate of 19 cases IV stage was 36.84% (7). The corresponding intra-groups statistical difference of 3 stages was significant by χ2 test (χ2 = 1.72, 19.03, 6.87; P > 0.25, P < 0.005, P < 0.01). The effective rate was 91.67% (44) in 48 cases undergoing total thyroidectomy; the effective rate was 53.85% (21) in 39 patients undergoing subtotal thyroidectomy. There was a significant difference between the two groups above by χ2 test (χ2 = 16.291; P < 0.005). Conclusion: The efficacy of 131I ablation of stage I and stage III in postoperative PTC patients was almost alike, while the efficacy of stage IV descended markedly. The results was mainly determined by residual thyroid tissue size because of different surgical modus. Objective: The aim of this study was to compare the effect of 131I therapy of different clinical stages in postoperative patients with papillary thyroid carcinoma (PTC). Methods: Eighty-seven PTC patients after surgery ablated with high doses of 131I from 2004 to 2010 were retrospectively reviewed. The efficacy of 131I therapy was assessed by three diagnostics that serum thyroglobulin (Tg) was normal or significantly reduced, 131I whole body scan (131I-WBS) was negative or the metastases shrank or the number of them decreased and new metastases was not found in cervical ultrasound examination. The χ2 test was used to analyze 3 factors which might affect the therapeutic efficacy of 131I in patients of different clinical period, including different surgical ways (total or subtotal thyroidectomy along with half or double sides neck lymph node dissection ), age (<45 years and ≥ 45 years) and ablative 131I dose. Results: Of 87 patients, the effective rate of 46 patients I stage was 89.13 The effective rate of 22 cases III stage was 77.27% (17); the effective rate of 19 cases IV stage was 36.84% (7). The corresponding intra-groups statistical difference of 3 stages was significantly by χ2 test The effective rate was 91.67% (44) in 48 cases undergoing total thyroidectomy; the effective rate was 53.85% (21) in 39 patients (χ2 = 1.72,19.03, 6.87; P> 0.25, P <0.005, undergoing subtotal thyroidectomy. There was a significant difference between the two groups byχ2 test (χ2 = 16.291; P <0.005). Conclusion: The efficacy of 131I ablation of stage I and stage III in postoperative PTC patients was almost alike, while the efficacy of stage IV descended markedly. The results was mainly determined by residual thyroid tissue size because of different surgical modus.