A simple gas chromatography method using flame ionization detector has been developed and validated for the quantitative determination of trace level of oxalyl chloride(quantified as diethyl oxalate) in Zolpidem tartrate drug substance. Efficient chromatographic separation was achieved on DB-35 capillary gc column, 30 m long, 0.53 mm internal diameter with 1.0 μm film thickness, employing programmed temperature with split mode (1:2) and run time was 60 min. The optimized method was validated for specificity, precision, linearity, robustness and accuracy. The obtained detection and quantitation limits of oxalyl chloride were 3 μg/g and 9 μg/g respectively. The method was found to be linear in the range between 9 μg/g and 750 μg/g with correlation coefficient 0.9996. The obtained average recovery of oxalyl chloride was 99.5 %. The detailed experiment results are discussed in this research paper.