The analysis theory of uncertainty and the assessment method of uncertainty factors in type A and type B were introduced.The uncertainty analysis model of boiler thermal effciency was established.Moreover

the calculation methods of sensitivity coefficient

normal combined uncertainty and extended uncertainty were put forward.On this basis

a 600MW unit coal-fired boiler was taken as the example to investigate the effects of each factor's measurement uncertainty on test quality of the boiler thermal efficiency.To avoid the secondary measurement uncertainty

the uncertainty factors with incompletely independence and the sensitivity coefficient by conventional imprecise numerical calculus were eliminated.The results indicates that

the parameters having significant contributions to test quality of the boiler thermal efficiency are unburned carbon content in fly ash(Cfh)

average exhaust temperature(tpy)

ash content as-received basis(Aar)

low heating value as-received basis(Qnet

ar)and fly ash content(fh)

in a decreasing order;and the neglectable parameters are nitrogen content as-received basis(Nar)

sulfur content as-received basis(Sar)and surface radiation and convection loss(Q5).Therefore

in order to improve the test quality of boiler thermal efficiency distinctly

it is worthwhile to lower the uncertainty of the significant parameters.