Abstract: The mining face under sea area of Beizao Colliery in Longkou Mine Field is the first mining face under sea area in China and the first full-mechanized caving mining face under sea area in the world.In this paper,the status of mining under water and sea area at home and abroad is briefly stated and the stratum,hydrogeology,tectonic,roof and bottom conditions are introduced in detail,ANN is adopted to forecast the height of leaking crevice belt in full-mechanized caving mining,the advantageous and disadvantageous conditions for the first full-mechanized caving mining face and the safe technique measure which is should be used are analyzed.All these can be concluded that the full-mechanized caving mining of the first mining face is feasible.