To probe the effect of different plant roots on dynamic change of soil moisture and its evaporation process,soil moisture evaporation under several thickets was compared in Guizhou karst plateau.The results showed that as for the change of soil water holding capacity,roots had no significant difference between Berberis aggregate and Cotoneaster horizontalis var.perpusillus,and the maximum soil water holding capacity was Berberis aggregate=Cotoneaster horizontalis var.perpusillus>Cotoneaster dammerii>no bushes;Soil water holding capacity was reduced with the passage of time gradually but its moisture effect was not consistent for different plant roots.With the change of soil moisture cumulative evaporation,it increased with passage of time gradually but its change was different for different plant roots.10 days of the total soil water evaporation in several bushes had the same change trend with the soil maximum moisture capacity.Based on the exponential function model for soil water characteristic curve in several bushes,there was a good correlation between soil water content and soil moisture evaporation time,and the degree of fitting was higher.