Based on the experiments, the relationship among draw-point size, released volume, and granular flow parameters are analyzed. Then, the improved stochastic medium theory of drawing(ISMTD) considering the effect of draw-point size is put forward. ISMTD shows the relationship between granular flow rules and size of stoping drift in sublevel caving and indicates the influence scope of draw-point size. Then two methods, namely the stochastic medium theory of drawing(SMTD) and ISMTD, are compared by three experiments in three different mines. The experimental results show that ISMTD can well reflec...