Based on the "blackout", the physical model of "free space-plasma layer-free space" is established. On the basis of this model, the analytical method is used to simulate and study the relationship between plasma absorption rate and electromagnetic wave frequency under the premise of different thickness plasma layer. The absorption of left-handed and right-handed circularly polarized waves by plasma layer and the one-way attenuation of electromagnetic waves in plasma were studied by changing the electron density, external magnetic field intensity and electron collision frequency, respectively. The results show that the absorption characteristics and one-way attenuation of electromagnetic waves by plasma change with the change of plasma layer thickness, electron density, external magnetic field strength, and electron collision frequency. The simulation results can be used as a reference for reducing the absorption rate of plasma layer and alleviating the problem of the "blackout".