The terrain of Changgang is rugged and mountainous, with the Kangnam Mountains in the northeast and the Chogyuryong Mountains in the southwest. The highest peak is Kumpasan (금파산, 1918 m) along the northern border.
Changgang is served by road and rail, with the Kanggye Line railroad passing through the southeast. There are soft-drink and pharmaceutical factories in the county. Rice is grown along the Chongsong River (종성강); other grains as well as grapes are grown in the highlands. Zinc is mined.