Objective：To study the relationship between the changes of pulse oxygen saturation（SpO2），pulse rate，and pulmonary function in daily activity of patients with chronic obstructive pulmonary disease（COPD），and to evaluate the value of pulse oxygen saturation monitoring during daily activity in distinguishing stable COPD and acute exacerbation of chronic obstructive pulmonary disease（AECOPD）. Methods：A total of 64 patients with stable COPD and 54 patients with AECOPD were enrolled，and 24 subjects without respiratory diseases were selected as control group. Basic data were collected and the changes of SaO2 and pulse rate were monitored during daily activity. The difference of SpO2 and pulse rate in each group was compared，and the correlation between SpO2，pulse rate and pulmonary function in the stable COPD group was analyzed. Results：①During daily activity，the difference of SaO2 index（including the rest SpO2，the average SpO2，the lowest SpO2（SpO2L），the variation of SpO2（ΔSpO2），ΔSpO2 percentage，SpO2L/ΔSpO2）between AECOPD group and stable COPD group or control group was significant（P < 0.05）. ②ΔSpO2 ≥6.50%，ΔSpO2 percentage ≥ 6.20% had a certain diagnostic value for AECOPD. ③The difference of SpO2L/ΔSpO2 between severe COPD and mild to moderate was statistically significant. ④The average pulse rate of stable COPD was negatively correlated with FVC%pred. The average SpO2 was positively correlated with FEV1，but the other indexes were not significantly correlated with pulmonary function. Conclusion：①Patients with AECOPD were more likely to experience hypoxemia during daily activity，and the SpO2 drop is obvious. ②After excluding cardiovascular diseases and other lung diseases in patients with COPD，ΔSpO2 and ΔSpO2 percentage could be used as monitoring indicators for early AECOPD management. ③The decline in pulse oxygen saturation during daily activity in patients with stable COPD may be related to lung function impairment.