An effective method was established to determine the content of residual chlorothalonil in textiles by gas chromatography/mass spectrometry-selected ion monitoring coupled with ultrasonic extraction technique. Residual chlorothalonil in textiles was ultrasonically extracted using ethyl acetate as the extraction solvent. The extract was condensed and analyzed by gas chromatography/mass spectrometry in selected ion monitoring mode (GC/MS-SIM). The concentration of chlorothalonil was calibrated by the external standard method. Good linearity existed between the peak area and the mass concentration of chlorothalonil in the mass concentration range from 0.2 μg/mL to 42.8 μg/mL. The equation was A = 95,399ρ ? 50,848, with a correlation coefficient of 0.9999. The limit of detection was 0.1 mg/kg for chlorothalonil. The blank samples were spiked at three concentration levels, and the spiked average recoveries changed from 81.9% to 95.4% while the relative standard deviation (RSD) changed from 1.8% to 5.2%. The proposed method was simple, rapid, sensitive and the limit of detection could meet the limit requirements of relevant regulations. Commercially available textiles were measured by this method, and chlorothalonil at different concentration levels was detected in some samples.