Objective To observe the changes of serum thyroid hormone levels in patients with chronic obstructive pulmonary disease (COPD) and to analysis its clinical significance. Methods The serum levels of TT3, TT4, FT3, FT4 and sTSH in 84 COPD in-patients and 60 healthy volunteer controls were detected at on admission and two weeks after discharged by chemiluminesent microparticle immunoassay method. Results The serum levels of TT3, TT4, FT3 and FT4 were significantly lower in COPD patients than those in controls. On the contrary, the serum sTSH level in COPD patients was higher than that of controls. The ratio of abnormal TT3 and FT3 levels in the COPD group were higher than that of TT4 and FT4. The serum TT3, TT4, FT3 and FT4 levels in the COPD group were higher than those in AECOPD patients. Conclusion The changes of thyroid hormone level of COPD patients always show low-T3 syndrome. The hormone level changes may be used to guide the treatment and predict prognosis of COPD patients.