Calcium-activated chloride channels (CaCCs) control diverse functions in nociception,neuronal excitability, muscle contraction and epithelial chloride ion secretion.It is vital to study the gating mechanisms of CaCCs.Cytosolic Ca2+ ([Ca2+]i) and membrane potential dual dependence is CaCCs characteristic gating feature.Based on the characteristics of native CaCCs, we construct a physical model to describe the steady-state open probability of CaCCs, which is given by VC1 is the equilibrium potential for Cl-across the cell membrane, which can be calculated by the Nernst Equation.