Cl^－ channels are found in all of cellular and subcellular membranes which have been determined. As housekeeper, they play vital roles in many different processes, such as regulation of cell volume, pH, resting membrane potential and excitability. Because the classical electrophysiological investigation has not been able to clearly charactarize a macroscopic Cl^－ current, as was done for Na^＋，K^＋ and Ca²⁺ current, Cl^－ channel are ignored for many years. The recent explosion in knowledge of Cl^－ channel is owing the technical using of single channel recording and molecular biology. The ionic permeation, selectivity, gating and pharmacological properties as well as the molecular clone and structure of background Cl^－ channels, the most widely existed Cl^－ channel in biomembranes, are reviewed.