The mass transport deposits (MTDs) have largely-undulating top surface, which would affect post-MTD turbidity currents deposition and distribution. A systematic study on the MTD deposition is helpful for interpreting the deposit pattern of submarine fan. Based on 3D seismic data in the Qiongying continental slope of the northern South China Sea, the MTD sedimentary system, and its overburden deposits, and the impact of the top surface on post-MTD sedimentation were numerically simulated using the Flow3D. Results show that: ① the top surface of translational domain is flat and gentle, on which distributed broad-gentle troughs; and the top surface of the toe domain fluctuates greatly, forming an isolated troughs. ② On the top surface of the translational domain forms a large and continuous submarine fan, while a small submarine fan can form in the toe domain; the slip slope of local uplift can develop different-sized submarine fans. The terminal domain is a favorable area for large submarine fans formation. ③ The greater relief of the top surface, the more conducive to sediment unloading and deposit, and the larger submarine fan formation.