Abstract: Based on the externality principle of ecological economics, combined with the properties of quasi-public goods, external economy, external diseconomy and intergenerational externality of wetland ecosystem, the paper analyzes the causes of wetland degradation. The results show that the worsening of wetland shrinkage and declining ecological service function are mainly due to lack of correct understanding of wetland function and benefit, and cost spillover caused by unreasonable profit distribution mechanism as well. The positive externalities engaged in wetland conservation have not been compensated, while the negative externalities have not paid due costs. Therefore, it is suggested that diversified eco-compensation mechanisms be established according to local conditions.