In order to study the impact of cross-border transportation of biomass burning from peripheral areas on the air quality in Yunnan Province, a southwestern border province in China, during spring, specifically in response to the large-scale pollution process in Yunnan from April 1 to 18, 2024, three border cities in Yunnan Province, namely Mengzi City, Mangshi City, and Mengla County, were selected as examples. Ground-based particle laser radar network observations, combined with ground air quality data, meteorological data, and MODIS satellite remote sensing data, were used, along with the HYSPLIT backward trajectory model, potential source concentration weight trajectory analysis method, and other technical means, to analyze the spatiotemporal distribution characteristics and motion trajectories of pollutants and to evaluate their impact on the air quality in Yunnan province. The results show that in April 2024, there were numerous fire points in the peripheral areas of Yunnan province. Under the dominance of the southwest monsoon, the three border cities were prone to the cross-border transport of biomass burning from Myanmar, Thailand, Laos, and Vietnam during the period from night to morning, with a lag time of 1.5 to 72 hours and a coverage range of up to 2300 kilometers. During the pollution growth process, the air quality in Mengzi City was mainly affected by mixed-layer transport from Myanmar, Laos, and Vietnam. The transport from eastern Myanmar and passing areas led to an increase of about 30 μg/m³ in the ground PM_2.5 concentration in Mengzi City on the afternoon of April 6th. Mangshi City was mainly affected by surface-level transport and low-altitude subsidence from Myanmar and Bangladesh, while Mengla County was mainly affected by surface-level transport and low-altitude subsidence from Laos, Myanmar and Thailand. Overall, Myanmar has the greatest impact on the air quality of border cities in Yunnan Province.