Based on seismic reflection profiles and multi-beam bathymetric data, a large submarine landslide named Fangliao Slide is mapped for the first time off SW Taiwan. The Fangliao Slide occurred on the continental slope to the west of the Fangliao Canyon at water depths between 420 and 900 m. The seafloor of the Fangliao Slide has a gentle slope angle (~1 - 2°). The landslide covers an area of ~15 km length and ~10 km width and a volume of ~26 km³. The headwall of the landslide has ~30 m vertical offset at the southern flank of mud diapir MD7-1, and the sidewalls are bounded by fault A in the west and faults C and D in the east. The sliding area is composed of five bathymetric terraces, indicating that the slope failures have occurred several times. The Fangliao Slide can be divided into an upper domain and a lower domain, separated at the water depth of ~600 m where the gas hydrate off SW Taiwan becomes dissociate. The initial slope failure of the Fangliao Slide was probably linked to mud diapirism of MD7-1 and the slope failure in the lower domain was probably augmented by the gas hydrate dissociation. The seafloor morphology in the lower domain is therefore more corrugated than in the upper domain.