It is of great significance to explore the temporal and spatial evolution characteristics of landscape ecological risk in border mountainous area and reveal the impact of natural and human activities on the landscape ecological risk, so as to maintain international ecological security and guarantee the stability of regional ecosystem. Based on the land use data in 2000, 2010 and 2020 of 25 border counties in Yunnan Province, a landscape ecological risk assessment model was established with landscape pattern index. The spatio-temporal evolution characteristics of landscape ecological risk were analyzed, along with the impacts of natural, accessibility, and social-economic factors on the landscape ecological risk were measured by the geographical detector. The results showed that the landscape types in the study area were mainly forest land and cultivated land from 2000 to 2020. During the same period, the area of the forest land, grassland, wetland, glacier and permanent snow decreased, while the area of the cultivated land, shrub land, bare land, artificial surface and water increased. The mean value of landscape ecological risk increased continuously and showed significantly spatial self-correlation. The ecological risk was mainly at lower and medium level among the area, yet the proportion of land in low, lower and high levels of ecological risk decreased, while those in the medium and higher level increased. Annual precipitation, annual average temperature, distance from town, population geographic concentration index, and population economic geographic concentration index of inconsistency were the main factors affecting regional landscape ecological risk. The interaction between precipitation and average annual temperature, population geographic concentration index and population economic geographic concentration index of inconsistency, and annual precipitation and population geographic concentration index had greater impact on landscape ecological risk.