Objective Hemifacial microsomia (HFM), a congenital craniofacial malformation,is characterized by unilateral mandibular dysplasia. At present,the Pruzansky classiifcation is the most common descriptive classiifcation used clinically, which involves mandibular deformities. Although multiple classification systems have been proposed for HFM, a quantitative classification has not yet been proposed. This study intended to propose a quantitative classification for HFMaccording to the mandibular volume on the affected side.Methods Patients with HFM from January 2017 to January 2018 were included, and the A/U ratio (volume of the affected side/volume of the unaffected side) was measured. This study proposed a classification for HFM(mandibular-volume classification, MVC) according to the A/U ratio and compared the new classification system with the Pruzansky classification using consistency and correlation tests. Results A total of 48 patients were included. The results of MVC based on the A/U ratio were as follows: A/U>0.85, classiifed asmild; 0.73-0.85, as moderate; and <0.73 assevere;the weighted kappa value of the Pruzansky and MVC classifications was 0.616 (P<0.01). Conclusion The quantitative classification of HFMbased on the A/U ratio can serve asa viable evaluation index for patients withHFM and can provide a new reference index for determiningthe treatment plan.