Polar stratospheric cloud (PSC) is considered to play an important role in the stratospheric ozone depletion through heterogeneous reaction on PSC particles and denitrification due to their gravitational sedimentation in the cold stratosphere. Recent extensive researches have drawn detailed picture of composition, nucleation and various properties of PSC particles, especially the effects on ozone destruction. This paper reviews the recent advances in our understanding of PSC particularly about their compositions and nucleation processes, and also discusses the relation of PSC activity with global environmental change.