Abstract: Delineating the ecological protection red line (EPRL) is of great significance in coordinating development of territorial space and eco-environment protection, which is key to safeguarding national and regional ecological security. This paper applies six indicators from two aspects of ecosystem services and ecological sensitivity to evaluate the current status of the ecological environment in Jiangsu Province. We further establish a niche-fitness model to assess the matching degree between the actual ecological niche and the ideal ecological niche of the EPRL. Then the terrestrial EPRL is spatially delineated in Jiangsu Province. The results show that: (1) The area of extremely important zones of ecosystem services accounts for 18.83% of the total area of Jiangsu Province which are mainly distributed in the low hill in southwest and north of the province, marsh regions among Huai River and the Tai Lake basin. The area of extremely ecological sensitivity zones occupies 6.96% of the total area of the province, showing an obvious spatial distribution pattern of “more in the south and less in the north”. (2) The total area of EPRL on the terrestrial parts covers 17 406.68 km²,and the area of rigid EPRL and elastic EPRL accounts for 57.28% and 42.72%, respectively. (3) The spatial distribution of terrestrial EPRL presents a pattern of “one horizontal, one vertical and three regions”, which primarily includes the Yangtze River, the lake groups of the Chinese Grand Canal, the low hill areas in southwest and north of the province, and marsh regions among Huai River. Niche-fitness model can be used to effectively assess the suitability of ecological space and provide a scientific method to depict the EPRL. Hence, the results of this paper can provide a quantitative reference base for depicting and optimizing the terrestrial EPRL in Jiangsu Province.