The invention discloses an auxiliary fine and high concrete member platform shipping device and an assembling method thereof. The auxiliary fine and high concrete member platform shipping device is characterized by comprising a device body which comprises a steel platform and an auxiliary platform, a reinforcing frame is arranged on the steel platform and connected with a pier body, the steel platform is provided with a reinforcing device for reinforcing the part between the steel platform and a ship body, the top of the pier body is provided with a supporting device, the steel platform is provided with a reserved rectangular hole channel penetrating through a floor, and a reinforcing rod protruding out of the steel platform is arranged in the reserved rectangular hole channel. The assembling method of the auxiliary fine and high concrete member platform shipping device comprises steel platform assembling, reinforcing frame assembling, reinforcing device assembling, supporting device assembling and inner reinforcing assembling. According to the technical scheme, a fine and high concrete member is prefabricated on the auxiliary platform and the steel platform, transverse and longitudinal moving and sea shipping are finished through the platforms, the steel platform and the auxiliary platform are closely connected in a matched mode, stability of shipping is improved, and the safety and controllability of shipping of the fine and high concrete member are guaranteed.