Abstract: Based on the background of deep mining under thick unconsolidated formation of Longgu Mine, we analyzed the mechanism of ground movement and subsidence of mining under deep condition, and studied ground subsidence rule, established coupling model of three-medium: discrete medium on the bottom, elastic thin plate medium in the middle and stochastic medium of unconsolidated layer on the top of the layer. Through analysis of the movement characteristics of each layer, we deduced their subsidence equation respectively. Through linear superposition of subsidence value of each layer, we obtained the surface subsidence value of deep mining under thick unconsolidated formation. Comparing the subsidence value of this method and value of the whole model method with the measured results, we found that this model is more accurate to forecast the ground subsidence of deep mining under thick unconsolidated formation.