The multi-purpose auxiliary vessel is one of dredging construction critical facilities,which is mainly used to assist the large-scale dredger in the construction of the open sea reef.This paper demonstrates the development design of one type multi-purpose auxiliary vessel in the construction of the open sea reef,analyses its functional characteristics,general arrangement and the key points of the design,proposes the difficulties of design for this auxiliary vessel,and provides reference for design of the same kind of ship.