Abstract: The underground water-tight rocky cave oil storage is an advanced structure specially designed to store various oil products. The structure has a series of advantages such as that of stability, shock-proof property, airtightness, shielding, thermostability and environment protection. Not only is the cave storage required to be in the integral rock, but be kept forever below the underground water level, making use of the difference of the specific gravity between oil and water to prevent gas from getting out so as to be able to store oil.