Abstract: The determination method of percent content of the impurity influencing distillation range of benzene and substitute benzene was completed by capillary gas chromatography with OV-101 fused silica capillary column and flame ionization detector (GC-FID). The relationship between the boiling range of distillations and the percent contents of impurities in the distillations was established. The determination method of impurities can instead of measuring peak height in GB/T 3146-82 standard method and its procedure is faster and simpler than the standard method.