Abstract: In order to improve the efficiency and sensitivity of trace pesticide detection in environmental water, an automatic online headspace solid phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC/MS) was established for the detection of twenty-four common pesticides in water. The effects of extraction needle coating material, extraction temperature, extraction time and desorption time on the extraction efficiency were investigated, and the ion concentration in solid phase microextraction matrix was optimized. The results showed that the concentration-response linear relationship of 24 target pesticides was good, and the determination coefficients (R²) were all greater than 0.9950. The limits of detection (LOD) was 0.25-5.0 μg/L, and the limits of quantification (LOQ) was 0.5-10 μg/L. The recoveries were 86%-117% and the relative standard deviation (RSD) was less than 18%. This method is suitable for the rapid qualitative and quantitative determination of trace organophosphorus, carbamate, organochlorine and permethrin pesticides in water samples, and it has the advantages of convenience, high efficiency and high sensitivity. It could be used for the inspection and identification of material evidence in pesticide poisoning cases in environmental water.