Abstract: In order to study the law of ground subsidence and overburden failure induced by fully mechanized top coal caving under thick loess，the measurement of surface subsidence and deformation and the height of overburden failure are detected through the establishment of ground observation stations and hydro-geological drilling exploration in surface.A great number of field data from ground observation stations and hydro-geological drilling exploration are collected.It is shown that ground subsidence under fully-mechanized caving of thick loess moved intensively with steep subsidence curve.The converge of subsidence and deformation curve at the edge of basis grows slowly.Maximum subsidence velocity is higher，and mining influence scope is much too far away.The detection of overlying rocks damage indicates that the overburden failure is developed abnormally in mining with fully-mechanized top-coal caving system，and the height of the water conducted zone is directly proportional to the total mining thickness.The ratio of the fracture height and the mining thickness is obtained to be 19.75 at average.The research can provide technical support for controlling surface mining damage and roof water inrush in coal mining under water in loess region.

Key words: Fully mechanized top-coal caving, Ground subsidence, Overburden failure, Prevention and treatment