Soil erosion by snow or ice melt waterflow is an important type of soil erosion in many high-altitude and high-latitude regions. The snowmelt waterflow erosion process, affected by soil freeze and thaw, is highly dynamically variable. In this study, field experiments were conducted to investigate the effects of thawed depth of frozen soil profile on snowmelt waterflow erosion of alpine meadow soil in the spring. The experiments involved five thawed depths from 0 to 100 mm under two snowmelt waterflow rates of 3 L/min and 5 L/min. The unthawed soil or shallow-thawed depth of 10 mm significantly altered the runoff and sediment production mechanism, including a significant delay of the runoff generation time and change of hydrograph and sedigraph. When the soil was frozen, the topsoil was structured with large open voids, to retain water and impede flow. This resulted in runoff generation time that was greatly lagged and soil erosion in the initial stage that was inhibited. The relationship curve of runoff and sediment concentration showed two-stage patterns that characterized a limited sediment supply in the early stage and hydrodynamic-controlled processes in the later stage. The deep-thawed cases (≥ 30 mm) showed similar hydrograph and sedigraph patterns with unfrozen soil condition. The findings of this study provide guidance for the future improvement of erosion model of partially thawed soil. Keywords: snowmelt waterflow erosion; thawed soil depth; soil freeze and thaw; runoff generation; sediment rating curve