At present, the formation and exfoliation of oxide scale of heating surface tubes in (ultra) supercritical boiler are recognized problems. When the unit is in the maximum load (maximum temperature) running, these problems will be more obvious with the increases of running time and the design value of steam temperature. This paper analyzed the cause and accident potential of oxide scales formation and exfoliation, discussed the oxidation status on different pipes at heating surface in subcritical, supercritical and ultra supercritical units, as well as compared the oxidation status on heating surface tubes before and after oxygenated treatment for boiler feed water. Finally, the measures of comprehensive treatment and monitoring for oxide scale of heating surface tubes were suggested, which could provide references for the treatment of oxide scale in other (ultra) supercritical units.