The strengthening of the marine sector and the realization of carbon peaking and carbon neutralization goals urgently necessitates a shift in marine energy development toward deep-sea and intensive utilization. The offshore integrated energy island (OIEI) serves as an effective solution for resolving challenges in deep-sea power consumption and achieving the diversified conversion of energy forms. Based on a summary of international OIEI development models and their current status, this study reviews China's development foundation and analyzes challenges such as institutional fragmentation, technological bottlenecks, and the absence of a business closed loop. Drawing on a source‒grid‒load‒storage‒utilization integrated philosophy, the study proposes a comprehensive development model featuring energy conversion, multi-energy complementarity, and zero-carbon services. It outlines three differentiated pathways: a nearshore shared model, a mid-to-far offshore industrial fusion model, and a deep-sea off-grid model. Multi-scenario techno-economic calculations and sensitivity analysis indicate that the economic efficiencies of the three models exhibit significant nonlinear alternating evolution characteristics with increasing offshore distances, and the commercial feasibility of off-grid energy islands in the deep sea is highly dependent on the support provided by green fuel premiums and the carbon market mechanism. The study recommends leveraging marine resource endowments to formulate medium-to-long-term plans supporting OIEI development. It calls for mastering key core technologies, such as high-efficiency energy conversion and green fuel power equipment tailored for multi-scenario applications. Furthermore, the research suggests accelerating the deep cross-sector integration of energy, marine engineering, and shipping industries, as well as establishing international certification systems for green hydrogen, ammonia, and alcohols. Additionally, it proposes perfecting a commercial guarantee mechanism driven by incentive policies and carbon markets to advance the large-scale construction and high-quality development of China's OIEIs.