Abstract: Significant topographic heterogeneity in the West Kunlun Mountains has facilitated the development of numerous well-preserved, large-scale debris flow fans.This study quantitatively describes and analyzes the characteristics of giant debris-flow accumulation fans.Taking debris-flow basins along the G219 highway in the West Kunlun Mountains as the study areas, we conducted field investigations and statistical analyses to define and characterize giant debris-flow accumulation fans.And then we examined how geomorphic factors influence the formation processes of different fan types, and employed the Massflow numerical model to simulate the depositional processes of these giant accumulation fans.The results indicate that 24% of the debris-flow basins in the study area develop different types of giant accumulation fans (transverse, equilibrium, and longitudinal), which are characterized by ancient formation ages and low bulk density.Under geomorphic influences, equilibrium-type fans gradually evolve into either transverse or longitudinal types.The formation of transverse fans is primarily controlled by average slope gradient and outlet width, exhibiting significant lateral expansion in flow depth and velocity.In contrast, longitudinal fans are mainly governed by depositional zone length, with pronounced longitudinal distribution of flow depth and velocity.These findings provide valuable insights for the study and mitigation of giant debris-flow accumulation fans in plateau regions.