The invention relates to a normal-pressure argon displacement system comprising an argon supply system for providing a gas source for an operating cabin; the argon supply system comprises a liquid argon storage tank, a vaporizer, a pressure regulating device, a flow monitoring device and a heating device which are connected in sequence; the operating cabin is provided with a cabin door and an observation window; a gas inlet connected with an output pipeline is formed in the bottom of the operating cabin and is connected with an exhaust gas distribution device; argon is uniformly input to the bottom of the operating cabin by the exhaust gas distribution device; an operating flat plate is mounted inside the operating cabin and at the upper end of the exhaust gas distribution device; and a vent hole is formed in the operating flat plate. The normal-pressure argon displacement system is used under a manned environment; by using the system, the concentration of argon in the operating cabin can be effectively guaranteed to meet the welding requirement of a titanium alloy material, and meanwhile, the problem that gas displacement cannot be realized under the manned environment is solved; and the system is simple and reliable in structure.