The invention discloses a large-scale wind turbine installation vessel crane and an integral assembling method thereof. The large-scale wind turbine installation vessel crane comprises a cylinder body. A reverse roller apparatus is arranged on the upper part of the cylinder body. A reversing chassis is arranged on the upper part of the reverse roller apparatus. A gin pole is arranged on the upper part of the reversing chassis. An obliquely positioned industrial draw plate is arranged between two supports of the gin pole. One end of the industrial draw plate is fixed on the bottom of a first support. The other end of the industrial draw plate is a boom hinging point which is fixed on a second support. A supporting seat is arranged between the other end of the industrial draw plate and the gin pole. The top of the gin pole is a place for a pitching pulley. The place for the pitching pulley and the boom hinging point are connected to a floating crane through steel cables. The crane and the method provided by the invention have advantages of short production period and reduced cost.