The transitional space is a complex ecosystem, which has a certain impact on the survival and development of human beings. However, with the aggravation of resource utilization and the acceleration of urbanization, the ecological environment is more damaged and the ecological risk is increased. Therefore, it is necessary to establish a reasonable and scientific ecological risk assessment system. In order to reveal the comprehensive ecological risk situation in the transitional space of Guangxi, China, the representative southwest Guizhou-Beibu Gulf region was used as the study area. This research was based on multi-source data and DPSIR model, using a non-dimensional quantitative model for data standardization, and using subjective and objective evaluation methods to assign weights to 18 indicators. Finally, the OWA-GIS method was used to conduct a comprehensive ecological risk assessment of the region under different decision risks. The results show that: (1) The risk level was at high risk in karst areas and coastal areas of Beibu Gulf as well as areas with intensive human activities. The forest areas in Baise show low-risk levels under different risk perspectives. (2) Vulnerability-resources-disasters affect each other's ecological risks. The Chongzuo Karst area, Nanning urban area, Beihai and Fangchenggang have higher-risk levels. The comprehensive ecological risk presents a transitional distribution from a low-risk in the northwest mountainous area to a high- risk in the southeast coastal area. (3) The decision attitude ranges from optimistic to pessimistic, with a gradual increase in risk level as the risk factor increases. The central and southern regions are higher than those in the north, and the areas with better socio-economic development and frequent human activities have higher risk levels. In reality, decision makers must adjust the decision risk coefficients according to different decision goals to obtain reasonable decision results. © 2021