Maxillary arch constriction is a common malocclusion of maxillary transverse hypoplasia in orthodontic patients. For children and adolescents with maxillary constriction, early maxillary expansion assisted rapid maxillary expansion is the first choice for the treatment of maxillary transverse hypoplasia. For patients with maxillary transverse deficiency, the best time to find the mature stage of median palatine suture is the decisive factor for the success of maxillary expansion. At present, there are many methods to evaluate the state of median palatine suture in clinic. This paper reviews the methods used to evaluate the state of midpalatal suture in the existing literature to provide reference for orthodontists' clinical decision-making.