Abstract: With the analysis on the major features of the mine pressure behaviors occurred in the fully-mechanized top coal caving mining face in the seam witha t hickness below 10 m or over 10 m, the mine pressure behavior occurred in the fully mechanized top coal caving mining in the seam with a thickness over 10 m would b e serious and periodical.The top coal would have play an important role in the mine pressure behavior of the fully mechanized top coal caving mining and under the roof deformation pressure role, the top coal would be converted to seemed rigid top coal.The top coal would form a structure of combined suspended boom beam-articulated rock beam, the periodical movement of the structure would cause small and large periodical roof weighting phenomenon occurred in the coal mining face and the occurr ence mechanism was stated.With the theoretical analysis, the analytic formula for the working resistance low limit value of the powered support was obtained. The major influence factors of the working resistance of the powered support analyzed would be the rock block length and thickness of the direct roof, failure step distance and thi ckness of the basic roof, rigidity of coal rejects, broken angle of the rock strata and broken swelling coefficient.