The invention discloses a novel electric multifunctional oral cavity mouth gag. The mouth gag comprises a main body shell, wherein the main body shell is divided into a front area and a rear area; andan upper supporting plate is arranged at the top of the outer side of the front area, a lower supporting plate is arranged on the middle lower portion of the outer side of the front area in a slidingmode, sliding rails used for sliding rods to be installed are arranged on the two sides of the inner side of the front area, and the lower supporting plate is detachably installed on the sliding rods. The mouth gag has multiple functions, can simultaneously realize active and passive opening-closing continuous movement of an oral cavity and accurate maintenance of the opening degree, and has multiple purposes of auxiliary opening treatment, training rehabilitation, auxiliary maxillofacial repair design and the like; the operation is simple, continuous movement, positioning movement and fixedmaintenance of the oral cavity supporting plates are achieved only by operating a button switch with one hand, the operation time is shortened, and the result precision is improved; and the mouth gagis high in universality, the supporting plates of different sizes or structures can be flexibly replaced according to the characteristics of patient groups, the mouth gag can be used for patients of different groups, and meanwhile the operability of the mouth gag is improved.