Abstract: Iso Nonyl Alcohol is a petrochemical. It contains complex chemicals which is isomers of alcohols from low carbon numbers to high carbon numbers. These chemicals affect the quality of Dinonyl O-Phthalate which is made from Iso Nonyl Alcohol and OPhthalic acid. After a lot of test, We found out the complete analytical condition that GC/MS analyse qualitatively and the GC analyse quantitatively the Industrial Iso Nonyl Alcohol using capillary colume. A Purity analysis method of Industrial Iso Nonyl Alcohol was established. After confirmation, the method is accuracy, rapidity, good repeatability and reproducibility. The method is first establishment in China.