The components of four kinds of JP-10 aviation fuels were analyzed by gas chromatography/mass spectrometry (GC/MS). The linear scope of gas chromatography was researched. The purities of JP-10 fuels were measured with an external standard method. Results show that JP-10 aviation fuels contains not only the main component exo-tetrahydrobicyclopentadiene, but also decahydronaphthalene, endo-tetrahydrobicyclopentadiene, adamantane and their methylated products, etc. The suitable concentration range for external standard method to measure the purity of JP-10 is 0.5-20 mg·mL^-1. This method is reliable, accurate, and can be used for determining the purity of JP-10.