Based on seismic survey, well logging and core observation, this paper interprets the sublacustrine fan of Liushagang Formation in Fushan depression. The formation of the sublauctrine fun can be attributed to two factors: the main factor is that the front of the delta entered the deep lake area along the southern slope under the action of the gravity. The second factor is that the channel sand close to the steep margin of the basin entered the deep lake area along the underwater channel, forming the gravity flow sedimentary underwater. Due to the different tectonic backgrounds and the degrees of material supply, the sublacustrine fan was mainly distributed in L1 and L2 periods, but was not well developed during L3 period. Viewed from spatial distribution, the sublacustrine fan was mainly developed in the northern and western parts, and the eastern part only possesses the secondary importance in this aspect. The extent of the fan in the north and the west is greater than that in the east, and the duration of the fan in the north and the west is also longer than that in the east. At the surface, the sublacustrine fan is distributed on the outer edge of the delta regime, and the sedimentary evolutionary sequence is in upward succession from sublacustrine fan through distal end of delta front to proximal end of delta front. The general sedimentary model of sublacustrine fan is like this: abundant braided delta sandstone migrated from the south to the north, deposited in the deep lake, and formed an isolated and big sublacustrine sandbody. The secondary material sources from the west and the east formed the sublacustrine fan in the deep lake under the control of the main active faults in the east and the west.