The rapid development and growth of urban agglomerations in China are accompanied by huge ecological costs. From the ecological constraint perspective, this paper proposed a three-dimensional measurement model of "quantity-efficiency-structure". We comprehensively used the ecological footprint, ecological carrying capacity and information entropy model to evaluate the sustainable development potential of towns in Fujian Triangle in 2018 from three aspects: resource supply and demand relationship, development ecological efficiency, and ecological structure. The influencing factors and urban transformation path were also explored. The findings are as follows. (1) The urban sustainable development potential in the Fujian triangle area has a great difference between the north and the south, inland cities and coastal cities. At the same time, a spatial agglomeration trend is forming. (2) Energy consumption and economic development level have a significantly negative impact on the sustainable development potential of towns, while factors such as population, urbanization, economy, and energy consumption have different impacts on the three subsystems of resource supply and demand, ecological efficiency, and ecological structure. (3) In view of the difference of influence mechanism, the paper classified the towns of the Fujian triangle into deficit, unbalanced, extensive and sustainable by the method of systematic clustering, and put forward the corresponding transformation development path according to the main development constraints of different types of towns. We hope to provide new ideas for the study of sustainable development of urban agglomerations and provide references for the transformation and development of towns in the Fujian triangle region.