Cutaneous mucormycosis is a rare opportunistic infection caused by zygomycetes that can be rapidly fatal if unrecognized. We describe the clinical, histopathological, fungal and molecular features of a case of gangrenous cutaneous mucormycosis. The patient presented with great necrosis on his right forearm at the site of detained intravenous cannula needle. He had type II diabetes and chronic renal insufficiency. KOH mount of black eschar showed many broad, aseptate fungal hyphae with right-angle branching. PAS staining of the tissue sample revealed similar broad hyphae in the dermis and cutis. Fungal culture and ITS sequence analysis identified this fungus as Rhizopus oryzae. As no organ involvement was detected, the patient was diagnosed with primary cutaneous mucormycosis. Considering the poor state of the patient, complete excision of the infectious tissue was performed without skin graft instead of amputation. At the same time, intravenous liposomal amphotericin B was given, starting from a small dosage and increased to a total dosage amount of 5.45 g. The wound recovered well with granulation. We emphasize that early recognition and prompt therapy including the control of the primary diseases were important. In this article, we also reviewed the features of primary cutaneous mucormycosis reported in China over the last 20 years.