The invention relates to a maximum extension distance quantified prediction method of a near-shore underwater fan flood sedimentation unit body. Based on a near-shore underwater fan sedimentation formation mechanism and a water tank sedimentation simulation experiment, plane and profile distribution characteristics of a near-shore underwater fan glutenite sedimentation unit body are determined, the longitudinal change rule of the thickness of the flood sedimentation unit body is researched, and a theoretical formula model of the thickness change of a central longitudinal profile of the flood sedimentation unit body is established; with the guidance of the distribution characteristics, determined by the simulation experiment, of the near-shore underwater fan glutenite sedimentation unit body, a practical geological body is divided into sedimentation unit bodies by means of well-seismic combination; and based on sedimentation unit body division, the boundary thicknesses of the flood sedimentation unit bodies are determined, and according to the practical well location condition on each sedimentation unit body, the maximum extension distances of the flood sedimentation unit bodies are predicted. According to the invention, the maximum extension distance of the near-shore underwater fan flood sedimentation unit body can be accurately and effectively determined, the sedimentation of a well network and the making of an exploration development scheme are effectively guided, and the well spacing efficiency in the exploration development process is improved.