The type-439 ferritic stainless steel tubing is typically used for a moisture separator reheater (MSR) in a nuclear power plant turbine system. MSR employ heavier wall tubing than that of other reheaters. Generally, service-induced damage can occur on the outside diameter surface of the type-439 ferritic stainless steel tubing, and the most typical damage mechanism is the vibration-induced tube-to-tube support plate (TSP) wear and the fatigue cracking. In this study, the optimized magnetic flux density of an eddy current probe for the inspection of type-439 stainless steel tubing has been analyzed, and a specific magnetic saturation probe was designed. We have successfully evaluated the capability of the magnetic saturation eddy current technique to detect and measure flaws in the type-439 stainless steel tubing of moisture separator reheater.