Abstract: The large-scale development of the carbon market has placed more stringent demands on the accuracy and comparability of carbon emission data from thermal power enterprises. China's current carbon accounting system, which mainly relies on the calculation method (emission factor method), faces challenges such as high risk of human interference and insufficient timeliness. The direct measurement method is gradually being widely accepted internationally due to its advantages of better timeliness, tamper resistance, and high automation. However, due to the lack of well-established system support, its comparability with calculation method results cannot yet be guaranteed. This study systematically compared the carbon accounting results of the calculation method (emission factor method) and the direct measurement method and evaluated the parameter uncertainty for seven typical domestic thermal power enterprises. The results showed that the average uncertainty of carbon emissions using the direct measurement method was 5.06%, significantly lower than that of the calculation method (6.88% when using measured elemental carbon content in coal). Within the calculation method framework, the data quality of measured elemental carbon content was significantly higher than that of measured lower heating value and carbon content per unit calorific value schemes. Moreover, measuring the carbon oxidation rate can reduce the accounting uncertainty by more than 50%. The proportion of measured parameters was a key factor in ensuring the consistency of results between the two accounting methods. When all parameters in the calculation method were based on measured values, the difference with the direct measurement method was only 2.51%, whereas using all default values resulted in a difference of up to 19.62%. From the perspectives of methodological comparison and parameter optimization, this study provides quantitative support for the mutual recognition of the two carbon accounting methods. It also offers key technical references for improving carbon data quality in the thermal power sector and refining the national carbon accounting system.