It is very important to investigate the relationship between analytical precision and concentration for quality control and assessment of analytical results. A set of analytical data of trace elements in soil and water deposits (Chinese certified reference materials) was studied for the relationship between the analytical precision of collaboration trials (i.e. reproducibility) and the concentration of the analytes. Iteratively reweighted least-squares (IRLS) linear regression, a robust method, was employed in this study. The linear relationship between the standard deviation and concentration was successfully established. On comparison with the conventional least-squares (LS) method , the results of IRLS linear regression are superior to those of LS.