¹³⁷Cs tracing technology and pollen analysis were jointly used to study sediment profile in a karstpeak-cluster grassland depression in Maolan,Guizhou Province.Vertical variations of ¹³⁷Cs,soil particlestructure and pollen composition in the profile showed that soil erosion in the grassland depression occurredin a relatively varied process from slight erosion to intensive erosion and then to rapidly decreased erosion.Those modern pollen of deposited sediment samples in the profile showed that the plant constitution dominated by fern seed,herb seed and tree seed changed to that dominated by fern seed and herb seed which adaptedto the karst rocky habitation.This means that herbosa including sparse Pinus plants degraded to herbosa inthe depression.Sediment deposition process is closely associated with plant regression and erosion environment change in the karst peak-cluster grassland depression.