Onychophagia, also known as chronic habitual nail-biting behavior, is a behavioral disorder characterized by repeatedly biting nails. It can not only cause damage to nails and cuticles, but also lead to oral diseases such as malocclusion, gingivitis, periodontitis, and temporomandibular joint dysfunction. The disease also exerts negative effects on patients′ psychological and social functioning, leading to feelings of shame and a decline in quality of life.Its diagnosis mainly relies on detailed medical history collection, observation of the patient′s nail-biting behavior and comprehensive examination of the fingernails (toenails) along with general skin examination. Differential diagnosis should include onychodystrophy, onychotillomania, onychomycosis (fungal infection), nail psoriasis, nail lichen planus, immune-mediated vasculitis and subungual melanoma. The treatment for onychophagia includes psychological behavior therapy, drug therapy, and traditional Chinese medicine therapy. Evidence for the treatment of onychophagia primarily comes from case reports. Multi-center, randomized controlled trials are needed to further validate the efficacy of these treatments, thereby providing a scientific basis for optimizing the treatment of onychophagia. This paper systematically reviews the epidemiology, pathogenesis, clinical manifestations, diagnosis and differential diagnosis, and treatment of onychophagia, providing reference for clinical diagnosis and treatment.