On the basis of mathematical model analysis,the independent active damping towards 3-DOF movement of mass center of the pneumatic isolation optical platform is put forward to cancel the re-coupling in multi-degrees of freedom system.The necessary conditions of the active damping and the way of velocity feedback are presented respectively.The realization as well as its block diagram of the 3-DOF active damping of the platform are described.The research results and its application are shown in detail.