Objective The genetic mechanism and sedimentary filling process of the Dongying Formation sublacustrine fan are unclear in the slope zone of the southeastern part of Bozhong Depression， which restricts the fine study of sublacustrine fan and deployment of well location in the study area， Methods From the perspective of source-sink system and three-dimensional seismic data， we semi-quantitatively analyzed the denude capacity and transportation path of the Bonan low uplift provenance. In addition， we clarified the characteristic sedimentary response and source coupling mechanism of a large-scale sublacustrine fan. We established the sedimentary filling process of a sublacustrine fan and summarized the development mode of a sublacustrine fan. Results （1） the Dong 2 subsequence is in the stage of lake-basin fracture-sink transition， which can be divided into two third-order sequences， in which the sublacustrine fan is developed in the highstand systems tract period of the lower Dong 2 subsequence； （2） during the period of lower Dong 2， the flux of denudation of the eastern section of the Bonan low uplift is larger than that of a sublacustrine fan. The detrital material provided by near provenances in the western part of the Bonan low uplift is unloaded under the depositional break of the slope along seven ancient gullies and five restricted ancient gullies. The coupling of near source supply， transport channel， and sedimentary slope break formed a large contiguous lacustrine fan deposit； and （3） the sedimentary filling process of asublacustrine fan is controlled by the location of restricted paleogeomorphology and the amount of space. Among them the early restricted paleogeomorphic formation can create large accommodating space， the sublacustrine fan sand body is preferentially unloaded. It formed the three major fan deposits， A， B and C. Owing to the spatial restriction of the two sides， the strong hydrodynamic conditions and seismic phases exhibit a chaotic down-cut channel superimposed on the lateral migration， and the formed fans are more sand-rich. With the entry of gravity flow with continuous replenishment in the later stage， the accommodating space gradually decreases， while the gravity flow along the replenishment channel overflows to the center of the open lake basin， forming two fans， D and E. Owing to the energy gradually weakening， the seismic phases have the characteristics of laminar strong-amplitude reflections， with the characteristics of the watercourse being inconspicuous， and the sand-richness is moderate. Late-stage source supply and energy is weak， and localized erosion and modification of seismic relative to early fan bodies exhibits weak amplitude reflections dominated by muddy watercourses. The large lake bottom fan has a spatiotemporal distribution and evolution pattern of early restrictive filling， middle overflow adjustment and late erosion and modification， which constitutes a developmental feature of lateral contiguous and vertical multi-phase superposition. Conclusions The three sectors， A， B， and C， below the first terrace are sand-rich and shallowly buried， with good conditions for oil and gas transportation and aggregation and excellent reservoir-cover combinations. The sweet spot area of sector C sector is large and has been an important target for the exploration of rocky reservoirs in the Bohai Sea in recent years.