Abstract: In the karst collapse zone of coal measures,the physical parameters of original hard and compact rock such as density,velocity,resistivity and so on change because of pore development.These physical abnormities cause the change of seismic wave field,inducing the change of the characteristic parameters of seismic wave such as velocity,reflection coefficient and impedance.The relation between velocity or density and porosity can be built based on Wyllie time average equation and density average equation,and then the relation between impedance and porosity can be built.The transmissibility of karst collapse zone depends on the pore development and continuity,therefore the porosity development in karst collapse zone in coal measures can be predicted using impedance attributes,providing foundation for judgment of water abundance.