Abstract: The simultaneous determination method for prochloraz and its metabolite 2,4,6-trichlorophenol in pepper was established by gas chromatography-negative chemical ionization mass spectrometry. The results showed that, high response for the detection of the targets in the chemical ionization mode was achieved, the purification effects of purification adsorbents PSA, C₁₈and GCB were compared, and C₁₈was finally selected as the pretreatment purification adsorbent. The limits of detection（LOD） was 0.05 mg/kg for prochloraz and 2,4,6-trichlorophenol. The recovery rate of prochloraz in pepper ranged from 85.0% to 92.3% and the relative standard deviation（RSD） was0.3% to 2.3%. While the recovery rate and RSD of 2,4,6-trichlorophenol were 82.3% ～96.4% and 0.8% ～1.7%,respectively. The developed method was simple, fast and efficient, and could be used for simultaneous detection of prochloraz and 2,4,6-trichlorophenol pesticide residues.