Abstract: The uncertainty evaluation method of potassium content of the test results of lithium fluoride by air-aetylene flame atomic absorption spectrometry was introduced and the mathematical model was established.The relative expanded uncertainty of the test results was obtained by the analysis and quantification of the various components of uncertainty in the measurement，which provided reliable theoretical basis for the accurate determination of the potassium content of lithium fluoride.

Key words: flame atomic absorption spectrometry, lithium fluoride, uncertainty