Abstract: For the study whether collapse column can conduct strong karst aquifer and lead to water inrush in coal floor or not, from the point of view of microscopic petrology, taking the collapse column in Taiyuan Gujiao Zhenchengdi Coal Mine as an example, mercury injection test and scanning electron microscopy （ｓｅｍ） are used to study collapse column fillings dissolution and pore structures. Results show that the porosity of rock sample fillings inside the collapse column is 0.640% to 3.830%, and the average pore diameter is 1.620 8 to 21.671 6 um, which is given priority to microporous and superfine hole. Collapse column are filled with a large number of calcite vein, and calcite crystal individual has corrosion phenomenon, corrosion is mild, the diameter of soluble denudation pores is far less than 10 um, the slightly soluble denudation holes in the current does not have hydraulic conductivity under the stress.