The Junggar Basin is a typical polycyclic superimposed basin in the Northwest China, which develops six sets of source rocks (Carboniferous, Permian, Triassic, Jurassic, Cretaceous and Paleogene) and contains six gruops of crude oil and three types of natural gas. The crude oils in the Northwestern Margin are basically similar and belong to the Group II oil. They have light carbon isotopic composition (δ13C<-29‰) and abundant carotenoids, isoprenoids, tricyclic terpanes and gammacerane. Steranes are dominated by C28 and C29 and there is nearly no diasteranes. These crude oils were derived from the Permian lacustrine source rocks. Most of the crude oils in the Central region of the basin are similar to those in the Northwestern Margin, but have difference in content of carotenoids, isoprenoids and gammacerane, which can be divided into four subgroups. These oils were derived from the Permian source rocks in different depressions. A small amount of crude oil has a heavy carbon isotopic composition (δ13C: -28‰ – -26‰) and Pr/Ph>2.5. The tricyclic terpane is mainly composed of C19 and C20. The hopanes are abundant but the gammacerane is extremely low. The steranes are mainly composed of C29 regular steranes and diasteranes. The oil was sourced from the Jurassic coal measures. There are five groups of crude oils in the Eastern Junggar. Group I crude oils have a very heavy carbon isotopic composition (δ13C>-26‰) and were derived from the Carboniferous source rocks. Group II crude oils are very similar to most of those in the Central region and were derived from the Permian lacustrine source rocks. Group III crude oils have a light carbon isotopic composition and are abundant in diasterane, Ts, C29Ts and C30 diahopane. They were derived from the Triassic lacustrine source rocks. Group IV crude oils come from the Jurassic coal measures. The mixed crude oil is a mixture of the Jurassic, Triassic and Permian oils, meanly accounting for 65%, 15% and 20%, respectively. There are four groups of typical crude oils in the Southern Margin, which belong to the Group II, IV, V and VI of crude oil, respectively. Group II and Group IV crude oils were derived from the Permian lacustrine source rocks and the Jurassic coal measures, respectively. Group V crude oils have a light carbon isotopic composition (δ13C<-29‰) and Pr/Ph<1.0. The gammacerane is abundant and has two isomers. The Ts, C29Ts, C30 diahopane, C27–C29 cholestanes and C30 methlysteranes are also abundant. They are derived from the Cretaceous lacustrine source rocks. Group VI crude oils, mainly low to medium mature oils, have a heavy carbon isotopic composition (δ13C: -28‰ – -26‰). The C27, C28 and C29 steranes are distributed in a V-shape. The dinosteranes are extremely abundant. They are derived from the Eocene lacustrine source rocks. Natural gas in the Junggar basin can be divided into three types, i.e. oil-derived, mixed and coal-derived. The first two types mainly come from the Permian lacustrine source rocks and the Carboniferous marine source rocks. The coal-derived gas comes mainly from the Carboniferous and Jurassic coal measures. The distribution of different types of oil and gas in the Junggar corresponds to the source kitchen developed in different geological ages. The Carboniferous oil and gas are mainly distributed in the Ludong-Wucaiwan area; the Permian oil and gas are widely distributed, mainly in the Northwestern Margin, the Central region and the Eastern area; the Triassic crude oil is limited to the Eastern area; the Jurassic crude oil is mainly distributed in the Eastern and Southern areas; the Cretaceous crude oil is mainly distributed in the middle of the Southern Margin; the Paleogene crude oil is mainly distributed in the western part of the Southern Margin. The Junggar basin can be divided into 5 petroleum systems, i.e. the Western, Central, Eastern, Southern and Ulungur petroleum systems, and 15 petroleum subsystems based on the structural features of the basin and the relations between source kitchens of different geolpgical ages and different types of oil and gas.