Objective To investigate the short term changes patterns of serum Tg and TgAb in patients with differentiated thyroid cancer (DTC) before and after the first 131I treatment and to explore the clinical value in patients management. Methods 80 DTC patients were included in this study, which include 22 male and 58 female (41.5±10.4 yrs), each of them was treated with 3.7～5.5 MBq of 131I. The serum Tg and TgAb levels were tested 1 day before and 7 days after 131I treatment. Meanwhile, post-treatment 131I whole body scan and 4～12 month follow-up data were also analyzed in order to evaluate the clinical significance of the short term changes of serum Tg and TgAb levels. Results The serum Tg levels in all patients were increased after the 131I treatment, but individual pattern and its relationship to the treatment outcomes varied significantly. In the group with serum Tg levels slight elevation (0～99 ng/L, 42 cases), relapse rate was 47.6%; The relapse rate in the group with serum Tg intermediate elevation (100～999 ng/L, 20 cases) was 60.0% and the relapse rate was 66.7% in the group with serum Tg levels high elevation (≥1000 ng/L, 18cases), that was significantly related with serum Tg levels increment. On contrast, the relapse rate (75.0%) was much high in the group with significant decrement of serum TgAb levels after 131I treatment as compared with the group with serum TgAb levels increment ( 43.8%) after the treatment (χ2=4.0，P<0.05). Conclusion The serum Tg levels increment in short term is useful in predicting favorable outcomes of 131I treatment, it might be same indication as the decrement of TgAb concentration in TgAb positive patients.