In this paper, a simulation model for the throttle orifice installed in the water wall of an Ultra-Supercritical Boiler is established based on the FLUENT numerical platform, and the verification has also been carried out just using the results obtained from the standard hydrodynamic calculating method. The scaling mechanism of the throttle orifice is analyzed, and effects of the throttle orifice's structural parameter on its scaling problem are studied by selecting different entrance chamfering, export chamfering, diameter and length. Finally, a method to reduce scaling is provided and a suggestion for the design of the throttle orifice is also made.