The stable operation of carbon market depends on the accuracy of carbon emission data

and the data quality of continuous emission monitoring system(CEMS)

as an adjunct to the accounting method

still needs to be improved. Uncertainty assessment is an important part of the construction of CEMS and data quality control.To assess and improve the data quality of CEMS

the uncertainty assessment of the carbon emission online monitoring data of an F-class gas unit was carried out. The results show that

the extended uncertainty of carbon emissions is 4.838%～5.012%(k=2)

and the main source of uncertainty is the flow rate measurement

in which the velocity field coefficient detection is the main reason for the high uncertainty in the flow rate measurement

and the operating load does not have a more obvious effect on the results. Therefore

improving the accuracy of flow rate and concentration measurement instruments or conducting regular calibration tests can effectively reduce the uncertainty and improve data quality.