Disclosed herein are a pump tower installation structure of a liquefied natural gas (LNG) storage tank and a manufacturing method thereof. The pump tower installation structure of the LNG storage tank includes an adaptor disposed at a predetermined area of an opening portion formed at an inner hull disposed on an upper side of the LNG storage tank, and a cover having through-holes corresponding to pipes of the pump tower installed at the storage tank, and disposed at a remaining area of the opening portion to be connected with the adaptor.