The influence of whey protein concentrate (WPC80) added to fermented skim milk drink on its stability was studied. The stability of fermented skim milk drink with different concentrations of whey protein concentrate was evaluated by particle size distribution, centrifugal analysis and Turbiscan analysis. The results showed that fermented milk drink containing 30% WPC80 had the smallest particle size and smallest centrifugal sediment. The turbiscan analysis showed distinctly that the fortified drink produced less sediment than the fermented milk drink with no added WPC80.