Polycyclic aromatic hydrocarbons (PAHs) are important geological records of paleoenvironment,paleowildfire and paleoclimate. The PAHs extracted from coal of the Shimengou Formation of Middle Jurassic in the northern Qaidam basin (NQB) were investigated by gas chromatography- mass spectrometry in this study. A series of 2- ring to 7- ring aromatic compounds were identified, including higher- plant- derived (cadalene, 6- Isopropyl- 1- isohexyl- 2- methylnaphthalene, retene, simonellite, dihydrogen retene) and combustion- derived PAHs (fluoranthene, pyrene, benz\[a\]anthracene, chrysene, benzofluoranthenes, benzo\[e\]pyrene, benzo\[a\]pyrene, indeno\[cd\]pyrene, benzo\[ghi\]perylene and coronene. These aromatic compounds indicate that the Shimengou coal were deposited in a lake swamp with brackish water environment accompanied by significant higher- plant input. These coals were at a relatively low thermal maturity stage (average Vr=0.56%). The higher- plant- derived PAHs are characterized by extremely abundant retene, moderate abundance simonellite, 2- methylretene and low abundant cadalene. These characteristics indicate that the vegetation was dominated by conifers (cypresses), and the climate was warm and humid during the during the deposition of coal in the Middle Jurassic in NQB. The abundant combustion- derived PAHs in the coal demonstrate the occurrence of intense wildfires during the Middle Jurassic in NQB, which may have been triggered by the high atmospheric oxygen concentration during this period. This study provides important molecular fossil evidence for the research of Middle Jurassic paleowildfire events in the Qaidam basin, and is also a useful supplement to the study of Middle Jurassic paleoenvironment and paleoclimate.