Abstract: The measurement uncertainty for the analytical results of major elements including Al, Fe, Ca, Mg, K and Na in soil and stream sediment samples determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) was evaluated. The main sources of measurement uncertainty came from sub-uncertainties of the analytical balance, analytical glassware, calibration solutions, calibration curves, reagent volume and repetitive measurements. Each subuncertainty was calculated and the composed uncertainty and expanded uncertainty of the measurement results were obtained by combining the sub-uncertainties.