Abstract: A mathematic model for evaluating the uncertainty of the determination procedure for silver in freelead solder in electric apparatus and toys by inductively coupled plasma-atomic emission spectrometry was established. The uncertainty sources for each of the parameters in the model were analyzed. The total uncertainty consists of partial uncertainties which came from weighing mass of the sample, calibration solution of silver, fitting of the calibration curves, volume of the sample solution used, reproducibility of the measurements and etc.. Each partial uncertainty of the measurement was analyzed and calculated. The combined uncertainty of 0.02% and expanded uncertainty of 0.04% were obtained.