Abstract: Aims The existence of dry valleys in the Three Parallel Rivers Area causes the interruption of vegetation belts, i.e., the "vegetation inversion" phenomenon, making it necessary to conduct a refined extraction of the vegetation vertical belts in this region. Despite extensive discussions on the vegetation distribution in this area, existing studies are often limited by data precision and extraction methods, failing to fully reveal the refined characteristics of vegetation vertical belts. Methods Based on the DEM-NDVI algorithm, combined with Landsat 8 OLI image data and NASADEM data, this study carried out a refined extraction of the vegetation vertical belts in the dry valleys of the Three Parallel Rivers area, and verified the accuracy of the algorithm to update the vegetation vertical belts in this region. Important findings 1)The spatial distribution characteristics of vegetation vertical belts at three different sections were determined, and the NDVI threshold values for the upper limits of each vegetation vertical belt at the north section were 0.61, 0.43, 0.10, at the middle section were 0.78、0.46、0.07、-0.05, and at the south section were 0.78、0.55、0.43；2)The width of the subtropical dry valley shrub-grassland belt, which serves as the base belt, gradually increased from the south section's 795m to the north section's 1161m. The width of the forest belt, which is the dominant vertical belt in the Three Parallel Rivers area, showed the opposite trend, gradually decreasing from south to north. The width and distribution area of the subalpine cold temperate shrub meadow belt and the alpine cold temperate sparse cushion vegetation belt in the study area were relatively narrow and small；3)The minimum altitude error of vegetation vertical zone extracted by DEM-NDVI algorithm is 3m, and the maximum altitude error is 43m, indicating high accuracy.This study provides basic data support and a reliable method for related fields, contributing to the advancement of research on mountain vegetation vertical belts.

Key words: Three Parallel Rivers area, dry valley, vegetation vertical belt, DEM-NDVI algorithm, refined extraction