A simple and sensitive High performance liquid chromatographic method was developed for the determination of trace level Benzyl chloride in posazonazole drug substance. The separation was achieved using Waters X Bridge C18(250X4.6mm,3.5µm) using mobile phase containing10mm Ammonium acetate PH:5.5 .The flow rate was 0.8ml/min and column temperature was 25°c.Benzyl chloride was detected using UV detector at the wave length 220nm.The Retention time was 13.7 min is for Benzyl chloride .The optimized method was validated to prove its performance characteristic by demonstrating selectivity, sensitivity (Limit of detection and Limit of quantification), Linearity, precision and accuracy. The limit of detection and limit of quantification of Benzyl chloride was found to be 3ppm and 10ppm for 20µl injection volume. The linearity of the method is found to be 0.1µg/ml to 0.75 µg/ml. Relative standard deviation of system precision, method precision is found to be 0.50% and 0.16% respectively. The accuracy of the method is found to be 97.5% to 99.7%.