Grassland ecosystems play an important role in the global terrestrial silicon (Si) cycle, and Si is a beneficial elementand structural constituent for the growth of grasses. In previous decades, grasslands have been degradedto different degrees because of the drying climate and intense human disturbance. However, the impact of grasslanddegradation on the distribution and bioavailability of soil Si is largely unknown. Here, we investigated vegetationand soil conditions of 30 sites to characterize different degrees of degradation for grasslands in the agropastoralecotone of northern China. We then explored the impact of grassland degradation on the distributionand bioavailability of soil Si, including total Si and four forms of noncrystalline Si in three horizons (0–10,10–20 and 20–40 cm) of different soil profiles. The concentrations of noncrystalline Si in soil profiles significantlydecreased with increasing degrees of degradation, being 7.35 ± 0.88 mg g−1, 5.36 ± 0.39 mg g−1, 3.81 ±0.37 mg g−1 and 3.60±0.26 mg g−1 in non-degraded, lightly degraded, moderately degraded and seriously degradedgrasslands, respectively. Moreover, the storage of noncrystalline Si decreased from higher than 40 t ha−1to lower than 23 t ha−1. The corresponding bioavailability of soil Si also generally decreased with grassland degradation.These processes may not only affect the Si pools and fluxes in soils but also influence the Si uptake in 

plants. We suggest that grassland degradation can significantly affect the global grassland Si cycle. Grasslandmanagement methods such as fertilizing and avoiding overgrazing can potentially double the content and storageof noncrystalline Si in soils, thereby enhancing the soil Si bioavailability by N17%.