Abstract: A mechanical model of cemented fills ceiling of underhand delamination heading is founded. Applying the principles of elastic mechanics and material mechanics, mechanical analysis of the two structures, namely, structure of hard support and weak slab as well as structure of weak support and weak slab, are elaborated in order to find the dangerous cross section and point of man-made intermediate ceiling. Such analysis throws light on the causes of mining accidents. The influences of elastic modulus of heading lateral walls on the stability of man -made intermediate ceiling is also analyzed by putting forward some measures to improve the stability of man-made intermediate ceiling.