Abstract: 13 stin muscles, 15 shoulder and flipper muscles, 8 pectoral muscles, 4 abdominal muscles, 13 neck, back and tail muscles of the Baiji, Lipotes vexillifer, are described in this account.There are two clearly defined sheets of the panniculus carnosus on both sides of the trunk. The outer, intermediate and inner layers of the maxillonasalis are not subdivided into anterior and posterior parts. The aponeurosis of the maxillonasalis externus has undergone hypertrophy to form a structure formerly referred to "floating bone" by Hinton and Pycraft, the maxillonasalis tendinous plate. The function of the latter concerns probably with the opening and closing of the blowhole and the adjustment of the vestibular air sac. The shoulder and flipper muscles are characterized by the presence of the trapezius and the absence of the triceps and coracobrachialis. The number of the shoulder and flipper muscles is half of that of the terrestrial mammals. The weight of the epaxial muscles which lie along the upper side of the backbone is two times of that of the hypaxial muscles.