Abstract: in order to determine the terminal location of the high level borehole in a gateway of a neighboring goaf in full -mechanized top coal caving mining face in a af island seam,based on No.30103 ful -mechanize top coal caving nining face in a af sand seamn of ShicuLan Mine as a studly objec a numerical fimulationmethod was applied to study the falure law of the overburden srata within150 ~ 175 m above No.30103 rul-mechanized top coal aing mining face. This resut thewed that the development sequence of the plastic:zone in the overburden strata of the cal mining face was obtined,which was steadiy developed from the midese cton of the coal mining face to the above strata of the cal mining face. Nhen the coal mining face was mining within adistance of 0 ~ 8o mthe hejghtof oo aing one in the coal mining face would be 16 ~ 21 m and the height of factured zone of the coal mining face woud be 21～ 43 m.According to therumericalsiyulato resis .the borehole terminal ocation of the high level borehcole designed would be at 25~ 35 m layer in the top oo ofthe cal mining fac.The borehoe d itributin sopewould be in 160 ~ 180 m scope above the coal mining face. The sie measurement anaysis showed that the drainage effect of the high level boreh ole was obvious andthe designed parameters were rational.