The invention discloses a method for centering a centerline of a subsection hull constructed in a two-island mode, which comprises the following steps: (1) reasonably dividing subsections; (2) arranging an involution line through subsection modeling; (3) drawing a centerline of a slipway, modifying the centerline after hoisting and positioning the subsections and drawing a high-accuracy centerline after a deck of the hull is run through fully; (4) preventing the subsections from sliding downwards and moving; (5) manufacturing and positioning the subsections; and (6) surveying the centerlines of the deck and a benchmark platform. The method ensures the accuracy of the centerline of the hull by controlling key points of each link in the design and construction. The application of the methodgreatly shortens shipbuilding period so as to greatly save manufacturing cost and achieve the aim of improving the speed of ship construction, and simultaneously compared with the centerline accuracyof the prior ships, the centerline accuracy of the hull is improved greatly.