Based on ecological carrying capacity and the relationship between ecological carrying capacity and other carrying capacity, the judgment standard and measurement object of ecological carrying capacity in late-developing regions were defined, the conceptual model of ecological carrying capacity in late-developing regions was also built, according to their sensitive eco-environment, relative slowness of socio-economic development, strong aspiration of development and late-developing strategy. The assessment method of ecological carrying capacity in late-developing regions was also established by multi-objective programming, combining with regional ecosystem health assessment. A case study was carried out in the economic zone on the west side of the Straits (called "Haixi Zone" for short), aiming at the sustainable development of key industry. Results showed that the human disturbance index of Haixi Zone was 2.68% in 2007, which is lower than the average level (3.13%) of China in 2006 and human disturbance threshold (5.96%) of Haixi Zone; the human disturbance index of all sub-zones of Haixi Zone was lower than its human disturbance threshold. Current human disturbance carried by ecosystem in Haixi Zone was relative light; human activities and key industrial development haven’t threatened regional ecosystem structure, service and its health status. According to the production rate of construction land in Haixi Zone, Haixi Zone and all sub-zones could sustain the present development of key industry, but Haixi Zone and most sub-zones wouldn’t sustain the medium and long term development of their key industry. As the production rate of construction land in Haixi Zone rises to 75% of the production rate of construction land in Shanghai city in 2007, Haixi Zone and most sub-zones would sustain the medium and long term development of their key industry. Therefore, the production rate of construction land is the key factor that influences ecological carrying capacity, the sustain development of key industry and ecological security of Haixi Zone. Meanwhile, there were spatial differences in carrying capacity and carrying status of ecosystem in Haixi Zone, which is helpful to sound development of social-economic, sustainable usage of ecosystem service and effective maintenance of ecological security.