The assessment of protected area management effectiveness is an important approach to achieving conservation goals. The management effectiveness should be assessed from multiple dimensions, including protected area management, ecology, and socioeconomic system, which could optimize the design and management of protected areas to meet their evolving demands. Based on the framework of the World Biosphere Reserves Decade Assessment, this study established a framework and indicator system for assessing the management effectiveness of Gansu Xinglongshan National Nature Reserve that located in the northeastern margin of the Qinghai-Tibet Plateau. The results showed that the final score for management effectiveness of Xinglongshan Nature Reserve was 82.68, indicating relatively high effectiveness, but there were still some issues. Among the five evaluation criteria—management foundation, ecological effectiveness, protection function, development function, and logistic function—the protection function received the highest scoring average (89.12%), while the development function received the lowest scoring average (78.72%). The scores for infrastructure and personnel allocation of rangers were significantly low, and the scores for development and governance in surrounding communities were also significantly low. The main issues identified in Xinglongshan included limited budget constraints and poor revenue generation for ensuring funding, inadequate number of rangers with low income, low level of community governance, as well as insufficient research capacity and gender equality. In the future management, it is recommended that protected areas like Xinglongshan Nature Reserve in the northeastern margin of the Qinghai-Tibet Plateau strengthen community governance, expand funding sources, and actively establish a network of natural reserves. The government should also provide support for establishing long-term partnerships between protected areas and research institutions in terms of future funding, thereby effectively enhancing the level of protection and management effectiveness.