Abstract: Oral mucoashesive drug delivery system delivers the drug into systemic circulation via internal jugular vein, thus avoiding acid hydrolysis in the gastrointestinal tract and first-pass metabolism in the liver and resulting in enhanced bioavailability and patient compliance. The key to successful oral mucosal administration is sufficient prolongation of residence time of drugs on the surface of biological mucosa to obtain higher and more stable drug absorption by the use of bioadhesion, i.e. the interfacial molecular adhesion between the surface of biological membrane and natural or synthetic polymers. This paper, reviewed the structural characteristics of oral mucosa, mechanisms of mucosal bioadhesion, factors influencing mucosal adhesion, design of oral mucoadhesive dosage forms and research progress in oral mucoadhesive drug delivery system.