Abstract: An efficient oil film damper,known as Porous Squrrze Film Damper(PSFD)is developed from the normal squeeze film damper(SFD)for effective and reliable rotor vibration control.The outer race of the PSFD is made of permeable sintered porous metal materials.The permeability of PSFD under squeeze effect makes it possible for the oil to permeate through the porous outer race,so that the characteristics of squeeze film forces are improved,in particular,as the amplitude of eccentricity is rather great.The nonlinearity of squeeze film forces could be reduced due to PSFD permeability,and the relations between oil film stiffness coefficient and damping coefficient of squeeze film forces could be improved.Investigation demonstrates that:The cavitated SFD high nonlinear oil film stiffness forces,which lead to many undesirable nonlinear vibration characteristics,lessen due to the permeability of PSFD,and the damping forces are relatively enhanced by PSFD.The nonlinear vibration characteristics of SFD system such as bistable jump phenomenon are greatly improved and even eliminated at higher unbalance level with the PSFD system.The PSFD can operate effectively under greater unbalance loads as compared with the SFD system.