Abstract: The off-site investment of enterprises in the context of flow space injects a strong impetus to the development of urban network, while ecological security affects the formation and structure of industrial investment network. The city cluster around Poyang Lake is a sensitive area of human-land conflict, and the natural ecological background has its uniqueness in the lake area. Taking the city cluster around Poyang Lake as the research area, we applied the research framework of city cluster flow space under the constraint of ecological security. The modified gravity model was used to examine the correlation strength of its industrial investment flow. The social network analysis method was used to explore the spatial correlation network characteristics and driving factors of its industrial investment under the constraint of ecological security. This study found that: ① the spatial network of industrial investment in the city cluster around Poyang Lake under the ecological security constraints had obvious characteristics of "centre-periphery", and the spatial linkage of industrial investment flows was strengthening. The structure of the network was becoming more and more stable; ② a small number of economically more developed regions occupied the centre of the network in the long term, and at the same time played the role of efficient intermediary. There existed the phenomenon of development path breakthrough in the peripheral areas; ③ There was a strong spatial dependence on the plate characteristics of the spatial network of industrial investment in the study area. The cities in the same plate showed the characteristics of embracing and warming up in geographic location; ④ The similarity of the level of opening to the outside world, the level of governmental regulation, the level of urbanisation of the population and the level of urbanisation of the land demonstrated a significant positive influence on the spatial network of industrial investment in the Poyang Lake City Cluster under the constraint of ecological security.