Abstract: Based on the experimental results in the previous paper, the mechanism of the hot corrosion behavior of alloy system Ni-16Cr-9Al-2W-lMo-4Co-(0~4)Ti-(0~4)Ta-(0~4)Nb (in at%) is investigated. In the Ti and Nb-rich comers, hot corrosion is controlled by the basic fluxing mechanism, and a dense and protective surface scale is formed which results in the better hot corrosion resistance for the alloys in these regions. While in the Ta-rich comer, the basic and acidic mechanisms function alternatively, which results in the catastrophic corrosion by forming the porous and non-protective scale, so the alloys in this region show poor hot corrosion resistance. In addition, the concept of "effective chromium content" seeraed to give a correct prediction of the hot corrosion resistance of such alloy systems.