Abstract: HPLC was applied to the determination of chlorpyrifos (~1%) “cockroach killing ointment” with a pretreatment of the sample by ultrasonic extraction.The effect of temperature and time on the rate of extraction were studied.The μ-Bondapak C18 (150 mm×3.9 mm,5 μm) was used as chromatographic column,and a mixed solution containing acetonitrile,acetic acid and water in the ratio of 82 to 0.5 to 17.5 (by volume) was used as the mobile phase,passing through the column with a flow-rate of 1.0 mL·min-1,UV-detection at the wavelength of 280 nm was used in the measurements.Tests for precision and recovery were made,and the values of RSD (n=6) obtained was 1.8% and of recovery in the range of 97%-105%,which were comparable with the gas chromatographic method.