Aim: This study was designed to observe the regulatory volume decrease (RVD) process of human lung adenocarcinoma cells A549 and to investigate its ion channel mechanism.Methods: Electric system of cell volume was used to detect the volume changes following exposure to hypotonic solution.Blockade of ion channels and the whole-cell recording mode of patch clamp technique were applied in the present study to clarify the role of the volume-sensitive Cl-channel in RVD.