Abstract: Based on the expanded mining area of Beizao Mine under sea was a three soft seam, in order to have a rational layout of the mine gateway and to solve the support difficulty problem of the mine gateway, the ground stress released and eliminated method was applied with the free space core pack stressmeter to have th e stress measurement to the expanded mining area under the sea.The analysis on the measured data showed that the ratio between the horizontal structure stress and the vertical stress in the expanded mining area of Beizao Mine under the sea was 1.56 in average, the ground stress field was mainly with the horizontal structure stres s and the direction of the max main stress was north to east about 45° .Therefore, the axial direction of the mine gateway was proposed to be possibly along the north-e ast direction of the layout.