The invention relates to an underground double-layered oil tank and a preparation method thereof and provides the underground double-layered oil tank and the preparation method thereof. The underground double-layered oil tank comprises an inner-layer steel tank and a housing, wherein a vacuum interlayer is formed between the inner-layer steel tank and the housing; a detection device for detecting the liquid leakage of the inner-layer steel tank and the housing is arranged in the vacuum interlayer; and the detection device is in remote-communication connection with a control room. The underground double-layered oil tank and the preparation method thereof have the advantages of simple structure, convenience in preparation, low production and maintenance cost, high automation degree, safe and reliable operation, short preparation period and the like, and is conductive to environmental protection.