Large conductance, Ca2+-activated K+ channels (BK channels)are widely expressed in various cells and tissues, which have the important physiological functions. Such kind of channels also has many biophysical properties of other members' in potassium ion channels family,, including the ion selectivity, the voltage-dependent gating, the ligand - dependent (calcium-activated) gating and the stress sensitivity. The structural analysis of BK channels can help to learn more about their own gating mechanism and the gating mechanism of other family members as well. Further more, with analyzing the commonness of the whole family members and the specificity of the BK channels, it will be helpful for us to illuminate the structure and the gating mechanism of BK channels.Based on the correlative study of potassium ion channels family, an in-depth discussion about the molecular structure, function and the gating mechanism of BK channels will be given in this paper.