Abstract: In order to evaluate short-term stability of opened stocks of certified reference materials (CRMs) in the analysis of volatile organic compounds (VOCs), CRMs LVOC-1RPM and SS-524RPM (including 54 VOCs and 2 surrogates in methanol, respectively, manufactured by ChemService Inc., USA) the stocks were transferred into 2 mL brown bottles equipped with Teflon-lined screw-caps, stored at -18℃ and protected from light. The variation of the CRMs’ compounds with storage time was tested by Gas Chromatography-Mass Spectrometry (GC-MS). The results showed that the standard deviations of all the compounds of the 2 CRMs ranged from 12-60 mg/L, the maximum relative standard deviation is 2.97% (n=5) and the maximum relative uncertainty is below 5.39%. In the 95% confidence interval, the chi-squared test (χ²-test) and uncertainty estimation show that precision and accuracy of the measurements is acceptable. In addition, the measurement deviation is not significant when the range of compounds of the CRMs are within (2000±128) mg/L. The experimental data also shows that the preservation period of the opened stocks of LVOC-1RPM CRMs is not more than 65 days and that of the opened stocks of SS-524RPM CRMs is not less than 65 days within the period of validity of the CRMs.