Abstract: This paper reports a method to analyze as many as 18 polycyclic aromatic hydrocarbons (PAHs) in airborne particulates by gas chromatography mass spectrometry (GC-MS) based on US EPA TO-13A standard. The selectivity of internal standards, the stability of data and the recovery rate of substitute standards are discussed. The internal standards were selected according to the correlations of response attenuation and response factors between internal standards and target compounds. The internal standard for BghiP, DBahA, IP and COR was d₁₀-PYL instead of d₁₀-AC, which was used in TO-13A. The stability of data and the recovery rates of substitutes of 365 samples for 7 days were studied. The instrument detection limit was 8-12 pg, the average error of target compounds were -11.21%-12.12%, and relative standard deviation (RSD, n=7) were 4.12%-14.27%. The recovery rate of substitute standards ranged from 64.35% to 127.94%, the average recovery rate were from 76.95% to 79.71% with the RSD (n=365) from 7.15% to 9.66%. In this paper, the stability of data, the recovery rate of substitute standards, etc. all met the requirements of EPA. This method can be used for batch or continuous analysis of 18 PAHs in atmospheric particulates.