An aeration pipe orifice device, which is connected with an aeration pipe on the base of a thermostat, is characterized in that an orifice block is arranged in the mouth of the aeration pipe. An orifice is processed in the center of the orifice block, the outer diameter transitionally fits the inner diameter of the aeration pipe, thereby resolving the problem. Since the orifice block adopted is in a simple structure, the inner diameter of the orifice on the orifice block added on the designed aeration pipe can be properly adjusted according to the performance requirements, and suitable profiled pipes can be selected according to a connecting pipe to match the outer diameter, thereby realizing the purposes of convenient processing and weight reduction as well as the prevention of leakage in the connection with a rubber pipe.