The Junggar Basin is a typical polycyclic superimposed basin in the Northwestern China, which develops six sets of source rocks (Carboniferous, Permian, Triassic, Jurassic, Cretaceous, and Paleogene) and are widely spread. The Carboniferous marine-terrestrial facies source rocks are distributed in most areas of the basin. The mudstone is mainly composed of Type II organic matter and has a medium abundance. The carbonaceous mudstone and coal have a high abundance but low-quality organic matter. The Permian lacustrine source rocks are widely spread, large in thickness, abundant in organic matter and high-quality in types. The kerogen has light carbon isotope and it is the main source rock in the basin. The Triassic lacustrine source rocks in the eastern part of the basin, mainly composed of Type II organic matter, have a relative high abundance in organic matter. The Jurassic coal measures, mainly composed of Type II2 and Type III organic matter, are organic-rich source rock. The kerogen has heavy carbon isotope. The Cretaceous and Paleogene lacustrine source rocks, mainly distributed in the southern part of the basin, have a medium abundance of organic matter, but are mainly composed of Type I and Type II organic matter. The Carboniferous source rocks are now mainly at high- and over-mature stages. The Permian and Triassic source rocks are now mainly at mature and high-mature stages. The Jurassic source rocks in most areas are at immature and low-mature stages and only those in the southern and eastern depressions are at mature and high-mature stages. As for the Cretaceous and Paleogene source rocks, only those in the southern depressions are now at low-mature and mature stages. To date, six groups of typical crude oils have been discovered in the Junggar Basin. They are quite different in geochemical features. The group I crude oil has a very heavy carbon isotope composition (δ13C>-26‰). The group II crude oil has a light carbon isotope composition (δ13C<-29‰). It contains abundant carotenoids, isoprenoids, tricyclic terpane and gammacerane. Steranes are dominated by C28 and C29 and there is nearly no diasteranes. The group III crude oil has a light carbon isotope composition (δ13C<-29‰) and is abundant in diasteranes, Ts, C29Ts and C30 diahopane. The group IV crude oil has a heavy carbon isotope composition (δ13C -28‰~-26‰) and Pr/Ph>2.5. The tricyclic terpanes are at low levels and is mainly composed of C19 and C20. Hopanes are extremely abundant, but gammacerane is at an extremely level. Steranes are mainly composed of C29 regular steranes and diasteranes. The group V crude oil has a light carbon isotope composition (δ13C<-29‰) and Pr/Ph<1.0. The gammacerane is abundant and has two isomers. The Ts, C29Ts, C30 diahopane, C27~C29 isocholestanes and C30 methyl steranes are also very abundant. The group VI crude oil, mainly low- and medium-mature oil, has a heavy carbon isotope composition (δ13C -28‰~-26‰). The C27, C28 and C29 steranes are distributed in V-shape. The C30 methyl steranes and dinosteranes are extremely abundant. The group II crude oil is widely distributed in different regions of the basin while the other groups of crude oils are only limited to some local areas of the basin. The Northwestern Margin of the basin is dominated by the second group of crude oil, which can be divided into three subgroups. The Central region of the basin is mainly characterized by the second group of crude oil, which can be divided into four subgroups. It also has a small amount of the fourth group oil. The eastern region has the first to fourth groups of typical crude oils and some mixed crude oil. As to the Southern Margin, four groups of typical crude oils (i.e. Groups II, IV, V and VI) and a small amount of mixed crude oils have been found there.