The transition from opacity to transparency of overdense plasma layers for the propagation of high-intensity laser pulses of circular polarization is investigated theoretically and by simulation. At some points,fluid equations cannot give a stationary solution,and then the kinetic aspects of the interaction should be considered. It is found that the regions where stationary solutions exist and therefore the plasma layer is opaque. It is also found that the opacity depends not only on the electron density and the laser intensity but also on the thickness of the plasma layer. The plasma layers become transparent where stationary solution do not exist, defined as absolute transparent. The electron density hardly changes because there is no light pressure acting on the plasma layer wehn the plasma layer is opaque.