Abstract: There are important Holocene geological relics in the Shenhu Bay Ancient Forest Natural Reserve. Understandings regarding the evolution process and time of the relics remain unclear. This paper study the K11 core collected in the Shenhhu Bay Reserve through lithology, grain size analysis, AMS¹⁴C dating, bioclast detection, and elemental geochemical indicators. It is believed that the ancient forest relics of the Shenhu Bay are the result of the ancient forest adapting to habitat changes under the background of rapid sea-level rise in the early Holocene. Its evolution process can be summarized into several stages: the initial growth period (before 8.6 ka B.P.), the period of aeolian sand accumulation and the growth-extinction of ancient trees (8.6～7.7 ka B.P.), and the period of preservation under tidal flat sediment (after 7.7 ka B.P.). The original growth environment of the ancient forest in Shenhu Bay might have been a low-lying incised river valley terrestrial surface. Around 8.6 ka B.P., the ancient forest area began to receive aeolian sand accumulation, and around 8.3 ka B.P., it started to transform from a terrestrial environment to a marine-terrestrial transitional environment. Subsequently, no earlier than 7.7 ka B.P., the invading seawater led to the extinction of the ancient forest and eventual burial and preservation under tidal flat sediments.