In the light of big floor deformation of roadway drove along goaf in fully mechanized top coal caving face in Xieqiao Coal Mine,based on the analysis of the integer stress distribution of roadway drove along goaf,a mechanical model of the roadway's floor was established.Through the analysis on the mechanism of floor failure of roadway driven along goaf,this paper points out that floor failure of roadway drove along goaf in fully mechanized top coal caving face mainly is caused by the effect of high stress in coal mass side,it is the key for controlling floor failure to improve the support of coal mass side,bottom corners and narrow coal pillar.This method has been applied to the engineering practice of roadway driving along goaf in 1101(3) fully mechanized top coal caving face in this coal mine,resulting in good effect of support.