Abstract: This paper uses the means of the deformation amount between roof and floor observation, the descending amount of piston observation and the load amount of pillar observation to research the strata-pressure behavior laws of Dafosi 40110 full-mechanized caving face in thick seam with in-situ monitoring. The result shows that first weighting interval of 40110 face is 91.8 m, the periodic weighting length of 40110 face is 55.5 m, the maximum dynamic load coefficient is 1.58 and the average descending amount of the whole hydraulic support piston is 6.98 mm.