Abstract: The paper deduces the formula of calculation criteria about extremely close distance coal seam by using elastic-plastic theory and the theory of slide line fields,determines the roof classification of the extremely close distance lower coal seam,and proposes the roof classification indexes of two hard condition very close coal seam face,the roof is divided into clip stone false top,cataclastic and block fractured roof three types.According to the characteristics of roof strata collapse of the upper coal seam under the condition of two hard and extremely close distance,the paper devides the roof collapse of the goaf of working face into full collapsed and non-fully collapsed,and deduces the load trength separately,which provides calculation method to ensure the overlying load when mine the underlying seam.