A GC method for the products in cyclopentene oxidation to form glutaraldehyde in a liquid-liquid phase transfer reactive extraction process, which was a new process, is presented. A model GC-103 gas chromatograph equipped with FID was used. The column is a SS tube(phi 3 mm x 4 m) packed with 13% SE-30 coated on 101 white silanized support and a SS tube(phi 3 mm x 2 m) packed with 9.1% PEG-20M coated on the same support. Operating parameters: column temperature programming, 70 degrees C(4 min), then 10 degrees C/min to 140 degrees C(6 min); injector temperature, 185 degrees C; detector temperature, 185 degrees C; N2, 45 mL/min; H2, 65 mL/min; air, 300 mL/min. By using this method, cyclopentene, intermediates, solvents, glutaraldehyde, and byproducts were separated properly. The yield of glutaraldehyde determined by this method is more reliable than that determined by the chemical method.