The maximum body length of the black sawtail hanger can reach 50cm. The fish body is gray or nearly black as a whole. There are certain differences in body color between juveniles and adults. The juveniles are brown-red as a whole.

Black sawtail cranes generally live in coral-clustered reef areas, and juvenile fish Most of them are scattered on reefs for food, while adults migrate in large groups between surge areas, mainly feeding on algae and benthic organisms.