The invention provides an installing method for a radial gate. A one-way portal crane, a cantilever crane and a winch are included; the one-way portal crane is fixedly arranged on the dam top which is further provided with the winch; the cantilever crane is arranged on the side wall of a dam body; and by means of cooperation of the one-way portal crane and the winch, segmented installation of supporting arms and a gate leaf is achieved. By adopting the structure, installation of the large radial gate is achieved through a method that the winch is matched with a self-control hanging beam, the installing cost of the large radial gate is reduced, and the installing efficiency is improved.