Abstract: In the GC-MS determination of polybromodiphenyl ethers (PBDEs), non-linearity between values of response signals and concentration of the analytes was encountered. Fitting curves as well as their correlation coefficients of the regression equations of 1st to 4th degree were comparatively studied. It was shown that the fitting curve of the quartic function gave the most satisfactory result. But considering both accuracy of determination and simplicity in statistical treatments using of the fitting calibration curve of 2nd degree was proposed for the analysis.