Abstract: Although the geochemical characteristics of colonial inclusions do not work as well as those of single inclusion in oil-and-gas origin and accumulation analyses, they are still reliable and important ways to study oil-and-gas origin at present. Studies of the geochemical characteristics of colonial inclusions in sandstone reservoir (Silurian, the Tarim Basin) and carbonate reservoir under salt layer (Ordovician, the Ordos Basin) indicated that, the biomarkers of crude oil from inclusions in sandstone reservoir (Silurian, the Tarim Basin) were the same as those of present saved crude oil which originated from the middle and upper Ordovician. The geochemical characteristics of gas in under-salt inclusions (well Longtan1, the lower Paleozoic, the Ordos Basin) were different from those of gas from the central gas fields. δ¹³ C₂ could not demonstrate natural gas origin due to big changes. The geochemical comparison between gas from inclusions and gas from gas pools proved that the natural gas found in the lower Paleozoic of the Ordos Basin was coal origin.