In order to avoid complex calculation of the partial derivatives in traditional uncertainty evaluation

and easily to evaluate uncertainty in measurement of regular performance test

a model for evaluating uncertainty in measurement of boiler's thermal efficiency has been established on the basis of Monte-Carlo numerical simulation method

and relevant calculation programme being compiled on the platfrom of Microsoft Excel.The said method has been used to analyse the demonstration case in "performance test code for utility boilers"(GB10184-88)

the uncertainty obtained is close to that given in the standard.The influence of error change in the input parameters upon uncertainty in measurement of boiler efficiency has been analysed

results show that the most affecting factors are discharged flue gas temperature

calorific value of the fuel coal

and ash content of the fuel coal etc..In order to reduce the uncertainty of test results

it is necessary to reduce the error of these parameters.