Glaciers in High Mountain Asia (HMA) are important water sources for millions of people in arid regions. However, their mass balance exhibits strong regional heterogeneity. The reasons are still not well understood mainly due to limited high-resolution temperature and precipitation datasets in high-altitude zones. Here, we propose a glacier ablation and accumulation index based on firn and snow observation from Sentinel-1 synthetic aperture radar data, which represent the seasonal ablation and accumulation patterns across HMA. Evaluations of the index with the summer snow line, precipitation, and temperature records from supraglacial weather stations confirm their reliability. Comparisons to available mass balance data show that glaciers with the lowest ablation and lowest summer-accumulation index which are located in the center of the HMA region, have the most balanced state (+0.05 m w.e. a-1). In contrast, glaciers with a high ablation and median summeraccumulation index, show highly negative mass balances (-0.47 m w.e. a-1). Under similar ablation index, the type of glaciers with higher summer-accumulation index is more negative. This work provides novel methods and knowledge to understand and project the glacier mass balance heterogeneity in HMA.