Abstract: A method was developed for the simultaneous determination of medium-chain chlorinated paraffins (MCCPs) and short-chain chlorinated paraffins (SCCPs) in leatherette by GC-ECNI-MS. Leatherette samples were ultrasonically extracted with n-hexane at 50 ℃ for 60 min, then purified with concentrated sulfuric acid, tested by GC-ECNI-MS, and quantified by internal standard method. MCCPs and SCCPs were quantified by the total response factor correction method, and the linear correlation coefficients were >0.99. The recoveries of blank samples of SCCPs ranged from 88.4% to 95.7% with relative standard deviations of 1.5%-3.0%. The recoveries of blank samples of MCCPs ranged from 88.3% to 103.2% with relative standard deviations of 1.6%-6.9%. The detection limit is 5 mg/kg, and the quantitative limit is 17 mg/kg, which can meet the requirements for the determination of MCCPs and SCCPs in leatherette.