Peatlands play a critical role in global carbon cycling, long-term ecological dynamics, and climate-carbon feedbacks, making their formation processes a key focus of global change research. The Ningshao Plain, a coastal lowland in eastern China, contains extensive Holocene peat deposits that developed mainly between ~7.0 and 2.5 cal ka BP. However, the mechanisms driving peatland formation in this region remain poorly understood. In this study, we present new diatom data from the well-dated T1041 profile at the Tianluoshan site in the Ningshao Plain, integrated with published pollen and carbonized seed records, to investigate the drivers of three mid-Holocene peat-forming episodes at 6.5–6.4, 5.2–5.1, and 4.4–4.3 cal ka BP. These peat layers formed under contrasting hydrological conditions, yet each is overlain by flooding deposits, likely associated with storm surges and/or extreme rainfall. Such event layers introduced substantial clastic materials into the wetlands, resulting in waterlogging and persistent anaerobic conditions conducive to peat accumulation. Our results indicate that peatland deposits in the Ningshao Plain constitute sensitive archives of abrupt hydrological responses to mid-Holocene weak monsoon events.