Tidal flat wetland is one of the most sensitive and fragile ecosystems in the world, and tidal flat reclamation plays an essential role for coastal countries or regions to expand land. In recent years, with rapid urbanization, tidal flat reclamation in coastal areas has led to a series of environmental problems such as wetland ecosystem degradation. Taking coastal wetlands in northern Jiangsu as a research area, based on the Environmental Kuznets Curve (EKC) model, this study attempted to characterize the process of tidal flat reclamation and socio-economic development, and reveal the phase of reclamation over the past 40 years, and explain the coupling relationship between tidal flat reclamation and social economic development. The results showed that the expansion of aquaculture water has been the main characteristics of reclamation in Jiangsu tidal flats in the past 40 years. Compared with Yancheng City, where aquaculture water bodies are clustered developing, Nantong City, which is represented by Qidong, has experienced a relatively complete tidal flat reclamation process for aquaculture water bodies. An exponential relationship was observed between the area of aquaculture water bodies and the regional fishery output value in Qidong, that is, when the per capita regional output value reached approximately 95,500 Yuan, the increase of regional fishery output value no longer depended on increasing the aquaculture water area through reclamation. There was a typical inverted U curve relationship between tidal flat reclamation and economic development in north Jiangsu coastal area in the past 40 years. The process of reclamation in north Jiangsu coastal area can be divided into three phases. In the early phase (1980-2005), the reclamation increased sharply with economic growth. In the middle phase (2005-2014), the increasing trends of reclamation and economic growth continued, with a turning point appeared, when the per capita GDP was about 3.64×10⁴ Yuan, and the maximum reclamation appeared with the speed up to 146.34 km²/a. In the late phase (2014-2018), tidal flat reclamation showed a downward trend while the economy still increasing. In the three stages, the relationship between reclamation and per capita GDP growth increased from 4.11 Yuan/km² and 17.08 Yuan/km² to 60.77 Yuan/km², showing a significant growing trend. Economic development, agricultural and rural economic reforms, and national and local policies make important impacts on tidal flat reclamation. The strictly national environmental protection policies would be of great significance to effectively control tidal flat reclamation and protect the coastal ecological environment.