The R-factor, representing rainfall erosivity, is a key determinant of soil erosion. However, inter-annual variability of erosivity in alpine canyon regions has been largely unexplored due to complex terrain and limited data, a factor that constrains effective erosion management. Here, we present a comprehensive spatiotemporal assessment of rainfall erosivity in the alpine canyon region of Southwest China using daily precipitation records from 38 rain gauges spanning 1980-2019. The average annual R-factor was 1709.85 MJ mm ha- 1 h- 1 a- 1, exhibiting an increasing trend of 1.83 MJ mm ha- 1 h- 1 per decade. Rainfall erosivity showed strong seasonal concentrations, with summer erosivity contributing over 60% of the total annual. A robust relationship was identified between erosivity density (ED) and high-intensity rainstorms (RS >= 50 mm day- 1; R2 = 0.81), confirming short-duration extremes as the dominant drivers of erosion risk. Mid-elevation zones (2000-3500 m) emerged as critical erosion hotspots. This validated regional-scale assessment provides critical guidance for soil and water conservation planning in topographically complex and ecologically vulnerable alpine canyon regions.