Abstract: The research on the marine resources and environment carrying capacity is the key to solve the contradiction between economic development and marine resources and environment protection. Based on the theory of diminishing marginal returns and short board, this study firstly constructed the theoretical framework and methodology system of marine resources and environment carrying capacity evaluation in two aspects, namely, the society development demand in a broad sense and the resources and environment constraint in a narrow sense. And then, we took the coastal waters of Changxing island in Dalian as the case study. The assessment of marine resources and environment carrying capacity in a broad sense was initiated based on the theory of diminishing marginal returns, taking zero marginal income of resources and environment development as the evaluation threshold. Meanwhile, the assessment of marine resources and environment carrying capacity in a narrow sense was carried out based on the short board theory, with three basic indicators, that were, sea space resources, marine ecological environment and uninhabited island resources and environment. Finally, the comprehensive carrying capacity was evaluated according to the above results. The results showed that the carrying capacity of Changxing island was overloaded in 2016. Based on the short-term, the reclamation of Changxing island had exceeded the optimal scale, so it had little promoting effect on social economic development. In addition, human's development and utilization activities of sea resources had led to serious loss of natural coastline, excessive development of sea area and unsustainable fishery resources.