Crooked mouth in big and small face may be related to habitual partial chewing, facial paralysis, maxillofacial gap infection and other etiologies. 1. Habitual partial chewing: when people have abnormal teeth, caries, apical inflammation, periodontitis, it will lead to the habit of chewing with the healthy side, resulting in the healthy side of the chewing muscles, bite muscles developed, manifested in the phenomenon of large and small face with crooked mouth. 2. Facial paralysis: If inflammation or tumor affects the facial nerve, resulting in facial neuritis or facial nerve injury, the facial nerve innervation function can be impaired and facial paralysis occurs, which is manifested as flaccidity of facial muscles on the affected side, and crookedness of the corners of the mouth on the large and small faces. 3. Infection of maxillofacial space: if wisdom teeth pericoronitis, apical infection and other untreated, there can be chewing muscle space infection, infraorbital space or buccal space infection, manifested as facial swelling, bilateral asymmetry, large and small face and crooked mouth phenomenon. There may be other reasons for the crooked face and mouth, so you should consult a doctor in time, complete the examination, clarify the cause and diagnosis, and standardize the treatment under the guidance of a professional doctor.