The invention relates to a method which adopts steel caissons to salvage a whole sunken ship. A GAPS and/or a super-short baseline are/is adopted to measure the coordinate; a steel caisson shaft with sandwiched shaft wall is manufactured according to the whole size of the sunken ship; after the steel caisson shaft is lifted and covers the sunken ship by adopting a hoist, sand filled in the sandwiched shaft wall of the steel caisson shaft is dropped to sullage at the outer margin of the sunken ship by using a static pressure sinking method; a bottom joist and a sullage-retaining plate are installed in bottom joist installation holes of the steel caisson shaft to form the steel caisson with the sealed bottom; then a sand-leaking hole cap is opened to discharge the sand inside the sandwiched shaft wall from a sand-leaking hole and saddle weights are dismounted to reduce the self-weight of the steel caisson; after being hoisted, the sunken ship is positioned on a semi-submersible barge to discharge the water. The method of the invention for salvaging the whole sunken ship is the static pressure sinking method with the steel caisson not swaying to the left and the right when being sunk; thus manual damages to the sunken ship can be reduced and the salvage time on the sea surface can be shortened; the risk and threat of the marine climate to the salvage workers can be avoided, and meanwhile, protection to the sunken ship and articles on the ship can be guaranteed to the greatest extent.