Abstract: In order to ensure the coal mining with size reduced safety coal and rock pillars under the water pressurized loose water bearing layer and the rational m ining in the seam of the water proof coal pillar,a surface geological borehole drilling,a CT technical detection of the underground sonic wave picking up layer and severa I other site measuring means with the dispersed element numerical simulation were applied to the study on the time space distribution law of the height development in the failure zone of overburden strata above the coal mining face with deep thick loose layer of the base rock for the fully mechanized coal mining face under the deep th ick loose layer of the thin base rock in Panji Mining Area of Huainan Coalfield.The study results showed that the failure zone in the overburden strata would be dynamic ally varied with the coal mining face to be pushed forward.With the pushing forward of the coal mining face,the height of the water flow cracking zone would be 35.20 ~ 45.10 m and the height of the falling zone would be 7.28~ 16.24 m.The failure of the overburden strata would be developed from bottom to the top and from rear to fron