Runoff dynamic parameters,sediment contents and soil erosion amounts of gully heads were studied in Yuanmou dry-hot valley by situ scouring tests under different runoff fluxes.The results showed that：（1）Under different runoff flow condition,Reynolds numbers obtained in gully head drainage area and gully bed were both greater than 500,which indicated the state of runoff flow belonged to turbulence flow.Their Froude numbers were greater than 1,which indicated the runoff flow was torrent flow.Resistance coefficient（f） obtained from drainage area and gully bed both in gully 1（without inner cavities in gully wall） and gully 2（with inner cavities in gully wall） decreased with the increase of runoff flow.Runoff erosivity（runoff shear stress,stream power,unit stream power） increased when runoff flux increased.（2）In the same runoff conditions,sediment content and soil erosion amount of gully 1 were greater than those of gully 2,which indicated that in the same conditions,the forming stage of cavities was more active than its successive stage in sediment yielding.（3）A positive correlation was found between soil erosion amount and runoff energy loss,Reynolds numbers,Froude numbers,shear stress,stream power,unit stream power of gully heads,and a negative correlation was also found between soil erosion amount and the runoff resistance coefficient（f）.