Abstract: An analytical method was developed to simultaneously determine inert ingredients, such asmethanol, toluene, ethylbenzene, O-xylene, para-xylene, meta-xylene, N, N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in pesticide formulations using gas chromatography-mass spectrometry. The method was applied to the detection of inert ingredients in 206 commercial liquid pesticide formulations. The pesticide formulations were diluted 10 000 times by acetonitrile, and the target inert ingredients were detected in selective ion monitor (SIM) mode. The linearity of 8 inert ingredients ranged from 0.999 2 to 0.999 8. The recoveries were between 76% to 116%, with the relative standard deviations (RSD) were lower than 17% at the spiked level of 100-1 000 mg/kg. The limits of quantitations (LOQ) were 100-500 mg/kg. The level of inert ingredients ranged from 0.5%-31.1% in 206 commercial liquid pesticide products. The content of inert ingredients in 7.2%-14.5% of the pesticide products were higher than the proposed maximum residue limits. High application rates of benzene organic solvents were detected in liquid pesticide formulations. This new method could supply reference for pesticide production, pesticide administration and fixation of maximum residue limits. Our results indicated that the usage of the harmful organic solvent in pesticides production was a noteworthy problem.