Since the middle of 1980's, the Iongwall top-coal caving technique has developed rapidly in China. At present, it is one of the main approaches in the thick coal seam mining. This paper describes some mechanics problems of the caving technique, such as the damage and failure of the top-coal, the strata behaviors in the caving face, and the relation of the support and the surrounding rock. In order to employ the caving technique in a widespread scope, the problems such as the caving technique in the hard coal seam, the moving and running of the loose top-coal, and the upper floating of the gas etc. should be systematically studied.