中文摘要：

生态保护红线是中国生态保护的一项重要创新，已被列为国家监管生态环境的重要政策。国家环境保护部于2015年发布了《生态保护红线划定技术指南》，确定了生态保护红线的划定方法，但是在识别生态保护红线边界时还存在一些技术难点。针对这一问题，本文探索了生态保护红线边界的优化方法。提出了生态保护红线边界优化遵循基本原则。以北京市昌平区为例，阐明了如何利用ArcGIS软件将划定生态保护红线的技术流程，包括评价各类生态功能区和敏感区，识别生态保护红线范围，准确定位生态红线边界3个主要步骤。最后通过对比优化前后的生态保护红线划定方案，阐明了该方法的可行性和存在的问题。

英文摘要：

The ecological protection red line is an important innovation in ecological conservation in China, and underpins a national policy for monitoring and managing important ecological environments. Guidelines for identifying the red line areas were issued by the Ministry of Environmental Protection of China in 2015. However, there are some technical difficulties in identifying the boundaries of the red line regions. This paper explores an optimization method to identify the ecological protection red line using the spatial analysis function of GIS software. Two initial principles are put forward： first, the boundary should be refined using higher resolution data when these boundaries are not within a nature reserve; second, the boundaries of the ecological protection red line should follow the boundaries of natural conservation areas. We applied the optimized method to identify the boundaries of the ecological protection red line using the Changping District of Beijing city as an example. The ecological functions of water conservation, soil conservation, sand fixation and biodiversity in the study area were identified and classified according to the rapid evaluation method on basis of net primary productivity （NPP） in the guidelines, and maps of their spatial distribution were produced. Then, spatial overlay analysis was carried out using the evaluation layers, and a comprehensive evaluation result was obtained by grading the evaluation output from the spatial overlay analysis. The preliminary design of ecological protection red line was established after removing some scattered small patches or merging the small patches into the adjacent large patches. Then, the preliminary design was optimized by overlaying a land use layer which had a higher spatial accuracy to identify the explicit boundary of the ecological protection red line region. The use of the high-accuracy land use layer transformed the low spatial resolution boundary to a high spatial resolution boundary after the overlay. Finally, the ecological pr