Abstract: In order to solve a deformation, support difficulty, high support cost and other problems of the mining gateway in the typical "soft roof, coal and floor" str atum of coal measures under Beizao Sea of Longkou, based on the full consideration on the soft and weak lithology of the coal measures strata under sea, poor binding degree, low strength, high swelling and creep phenomenon, the paper studied the material composition and structure features and the physical and mechanics propertie S of the surrounding rocks under the sea area and analyzed the advance support pressure distribution variation and the behavior law of the coal mining under the sea.A discovery practices were conducted on the support methods of the mining material gateway, transportation gateway (stage loader gateway of the transportation gatewa y) under the seam and good support effects were obtained.