LNG ship pump tower positioning and mounting method

The invention discloses a method for positioning and installing a pump tower of an LNG ship. The method specifically comprises the following steps that a liquid dome section and a deck section are manufactured; marking a first sample punching mark on the inner deck of the liquid dome subsection, and marking a second sample punching mark on the inner deck of the deck subsection; carrying the deck subsection on the cargo hold, and reversely connecting the second sample punching mark on the deck subsection to a ship body inner bottom plate of the cargo hold to determine the mounting position of the pump tower base; a pump tower base is installed, and the pump tower is hoisted on the pump tower base; hoisting the liquid dome subsection into the hole of the deck subsection, so that the first sample punching mark on the liquid dome subsection is aligned with the axis of the pump tower; and the liquid dome subsection, the pump tower, the cargo hold and the deck subsection are welded into a whole. The positioning and