Slot-check dams are widely applied to mitigate debris flow hazards in China. This paper aims at providing an analysis of their performance in the field and establishing a verification to evaluate the efficiency of the slot-check dam group and a single slot-check dam in sediment control. The study area is Shengou basin in Dongchuan district, Kunming in China, where debris flows directly threats the safety of more than sixty thousand people living in the major city. The analysis is based on a relatively detailed field knowledge consisting of topographical, sediment data and geometry of the group of five slot-check dams at Shengou basin. The results suggest that the conserving sediment volume of each dam has a close relationship with its relative location in the group, gradually decreasing from upstream to downstream. The channel slope has a little influence on the conserving effect. The accumulated sediment volume upstream a check dam strongly depends on its sub-catchment characteristics and increases with the controlled catchment area of the dam and the distance from the dam to the upstream most. A semi-empirical relationship between the conserving efficiency for each subsystem of the group, defined as the percentage of its conserved sediment volume, and the subsystem’s catchment parameters is developed.