The cause,mechanism and tentative control measures of mine earthquake in fully mechanized top coal caving mining are studied by case analysis. Because the coal caving height is larger in fully mechanized top coal caving mining,thick and hard rock strata at higher position turn into the main key stratum,which have large movement and higher impact energy. These enhance the possibility and harmfulness of mine earthquake. The mine earthquake is caused by many factors such as main key stratum,great structure,inadequate subsidence of step-shape gob boundary overburden,fault activation,stress concentration and reduction of long-time strength of section pillar. The great area breaking movement of main key stratum causes great structure unstable and gravity potential energy to be released at a large-scale degree. The superimposition of gravity potential energy and impact energy turns into impact kinetic energy,which causes mine earthquake by the work to surrounding rock of gob. Based on the reasonable layout of mining,the control techniques,for example,reasonable leakage wind,building embedding high strong buffer bulkhead or ┬-entry bulkhead,separating strata grouting under the main key stratum to reduce the subsidence,grouting into the O-shaped space in the gob,should be studied by experiments.