The fluctuation of on-line performance monitoring results is very large

this problem must be overcome in the technology of units' performance monitoring and diagnosis.The real signal of units' performance variation resulting from variation of operating parameters and equipment performance is drowned in many noises

leading to correct analysis results being unable to be obtained.For this

the units' thermodynamic parameters have been filtered by using the multiscale filtering character of the empirical mode decomposition.The fluctuation of units' heat consumption rate calculated by using the filtered data has been apparently improved

the fluctuation range being decreased from 2.5% to 0.3%

and the result correctly reflecting the trend of heat consumption rate variation along with the load.