Abstract: Color development of jet fuel during storage is one of the indications of fuel instability, and these dark compounds in jet fuel may be detrimental to aviation engines while running. In this paper, dark jet fuel sample of Pingba RP-3 was taken from an underground storage tank. Adsorptive gum was separated by adsorbing fuel through neutral alumina with size of 100-200 mesh and eluting with acetic acid and distilled water. The gum sample was analyzed with organic element analyzer, gas chromatography combined with mass spectrometry (GC-MS), Pyrolysis-GC-MS and Fourier transform infrared (FT-IR) spectrometry to identify the colored compounds. In addition, simulative accelerated storage stresses under modified ASTM D4625 and ASTM D2274 were carried out to investigate the storage degradation properties of Pingba RP-3. The results show that the dark materials in Pingba RP-3 are concentrated in adsorptive gum. The predominant colored compounds in the gum are alkylated hydroxybenzene (some in polymerized form), and there are trace nitrogen heteroatomic compounds and no sulfur contained chemicals in the gum. The oxidation reaction plays an important role in the formation of colored components and adsorptive gum during storage. Alkylated hydroxybenzenes may be the main precursors of colored materials in Pingba RP-3.