In order to study the clinical efficacy of facial artery musculocutaneous flap on repairing the defect of the floor of mouth, 21 patients had received this type of treatment from 1991 to 1997. The size of the flaps ranged from 8.0 x 3.4 cm to 12.1 x 5.4 cm and the average age of these patients was 59.5 years old. The donor site was closed directly. Nineteen flaps survived completely, while necrosis occurred at the apex of the other 2 flaps, which healed by ordinary management. The applied anatomy of the flap and the design and the main points of the operation were reported in details. The advantage of the flap and the prevention of facial malformation following operation were discussed. The conclusion was that this type of flap was ideal for reconstruction of the defects of floor of the mouth.