Abstract: The measurement uncertainty of the analytical results of B in groundwater samples by inductively coupled plasma-mass spectrometry (ICP-MS) was evaluated using continuous propagation model of uncertainty and the regression of x, y double error was used in the course of standard curve fitting. The main sources of measurement uncertainty include the sub-uncertainties of standard stock solution, the preparation of the standard series solution, repeated measurements and the fitting of standard curve. Compared with the uncertainty results obtained by the least squares linear fitting, the results obtained by the regression of double error are more accurate for relatively high concentrations.