This standard defines a test method for the determination of the purity of cyclohexane using Gas chromatography, CG by external standard technique. Suitable for cyclohexane production and quality control of set specifications, capable of detecting the purity of normal impurities, but limited ability to detect very high boiling points or abnormal impurities. The test method covers the analysis of impurities from 3 to 200 mg/kg with a detection limit of 1 mg/kg. This standard provides a scientific basis for ensuring the mass and conformity of cyclohexane, while specifying the rounding method of test results and the criteria for using SI units.