The authors developed a high performance liquid chromatography（HPLC）method to analyze Benzyl-dimethyl-dodecyl-ammonium chloride（BAC） from an extracted solution of preservative-treated wood.The parameters of this method were as follows: a venusil SCX separating column;a 5︰1 methanol to water volume ratio,ammonium chloride and acetic acid was used as a mobile phase;and a 262 nm wavelength UV detector.The linear correlation of this method was 0.999 7 at a 10 to 1000 mg/L BAC concentration.The average recovery of spiked samples was 100.9%.The relative standard deviation was 0.235% and the detection limit was 1.0 mg/L.