Through borehole drilled in the top rock

the bore observing system by bore resistivity method is formed; and the distortion and collapsing characters in the top rock of the working face can be tested dynamically during digging process. According to mining velocity the changing characters of electric field in different times can be gained. And the changing law of overburden failure affected by mining can be researched comprehensively. Limited by testing condition in the spot of laneway

through single borehole in the top rock the testing data have the full space effect

the explaining result and location for rock failure is affected in different extents. Its resolution for the law of overburden failure is decreased. Through model test and practical detection

the resistivity testing method using the single borehole in the top rock is improved. The bore-laneway resistivity method is formed through laying the poles in the laneway

and the binding character of the resistivity data is enhanced compared to the single borehole system in the top rock. It provides the base for the resistivity inversion and the height judgment of the two belts. The practical researching results show that the bore-laneway resistivity CT method has sensitive reaction to structure change affected by mining; and its resistivity section is clear and dynamic. The resistivity ratio section and background detection can resolve effectively the characters of the process in the coal mining. The explaining capable of the detection achievements for the overburden failure is improved. The result is helpful to renew the practice of the overburden failure.