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Ecosystem structure determines material circulation, energy flow, and system function. Based on field investigation data in the Sanmen Bay, East China Sea from 2017 to 2018, ecological channel model was constructed by Ecopath, describing energy flow routes and functional characteristics of the Sanmen Bay ecosystem. Results showed that grazing food chain was the main energy circulation channel, and the trophic level of each functional group ranged from 1 to 3.80. Energy flow of the system was mainly concentrated in the first five levels, with an average energy conversion efficiency of 13.0%. Energy conversion efficiency was 12.8% and 14.5% from primary producers and debris, respectively. Connectance index (CI) and system omnivory index (SOI) were 0.40 and 0.24 respectively. Finn's cycling index (FIC) was 0.40, and Finn's mean path length (MPL) was 2.06. The ratio of total primary productivity to total respiration was 13.59. In conclusion, Sanmen Bay ecosystem was immature in material circulation and energy flow. This work is helpful to understand the structural and functional traits of coastal ecosystems in China.生态系统的结构决定生态系统的物质循环、能量流动和系统功能。本研究采用Ecopath模型,根据2017—2018年中国东海三门湾海洋生态实地调查数据,构建了三门湾生态系统的生态通道模型,描述了三门湾生态系统的能流结构,分析了其功能特征。结果显示: 三门湾生态系统营养级范围在1~3.80,能流渠道主要表现为牧食食物链,系统能流结构主要集中在前5个等级,系统平均能量传递效率为13.0%,系统初级生产者的能量传递效率为12.8%,系统碎屑的能量转换效率为14.5%。系统连接指数与系统杂食性指数分别为0.40和0.24,Finn循环指数为0.40,系统的Finn平均路径长度为2.06,总初级生产量与总呼吸量之比为13.59,表明当前三门湾生态系统处于不成熟阶段。本研究有助于理解中国近海港湾生态系统的结构特征和功能特点。.