Darkhan-Uul aimag is surrounded with the low branch mountains of the Khentii range and located in the northern Mongolia at the north side of the Kharaa river which belongs to the Orkhon-Selenge river basin. The area is elevated at 700-1,500m above the sea level which is considered to be a relatively low area and the land surface is composed of multiplex of forest steppe and mountains. Although the total area of the aimag is not as large as the others, it is rich in gold, calcareous, coal, construction materials and such natural resources.

The aimag has a severe continental climate and belongs to the Central Khangai zone. The average air temperature ranges between +40°C to +5°С in the summer months and drops down to  -30°C to -7°С during the winter times. The annual precipitation is 3.2mm.

Soil
The most  part of the aimag is covered with mountain dark soil with some sediment soil formed with forest-dark and taiga soil.

Water covers 2,112.54 ha of the total area of the aimag and from this, rivers take up 1,998.0 ha, lakes take up 24.0 hа and industrial water funds take up the remaining 1.0 hа. Rivers such as Zulzaga, Sharyn Gol, Yeruu, Orkhon, Khuitnii and Khavchuun that are originated from the Khangai Mountains and flow to join the Orkhon river belong to this aimag.

Forest reserve occupies 79,012 hа of the territory of the aimag and wooded forest takes up 96.4% or 76,135 ha and non-wooded forest zone occupies 3.6 % or 2,877 hа of the total forest reserve of the aimag. Natural forest covers 61,672 hа while 2,458 ha is covered in bushes, 5,983 hа in scattered-forest respectively. 11 species of flora found in this aimag territory such as couch grass of steppe, thyme, feather grass, wild onion, also trees such as pine tree, birch, poplar, aspen, bush, elm, black alder tree, eglantine and dogwood. Moreover 9 species of wild fruits such black cherry, strawberry red berries, seabuckthorn and gooseberries are found here. The aimag is abundant in medical floras such as rooseroot, mushrooms, wild garlic and thyme.