Studying the transmission characteristics of high-frequency microwaves in plasma can effectively analyze and assess the information transfer process in microwave communication and radar technology. Numerical simulations were employed to analyze the effects of plasma electron density, thickness, and incident wave frequency on microwave reflection, absorption, and transmission. The results indicate that increased plasma thickness and electron density lead to enhanced absorption and reduced transmission; reflection increases slightly with decreased thickness and increased electron density. High-frequency microwaves are more easily transmitted through plasma, with transmission enhancing as frequency increases. Furthermore, the research shows that electron density not only affects energy transmission but also alters the electromagnetic wave shape, causing its broadening. High-density plasma significantly broadens microwave waveforms both spatially and temporally, with inelastic collisions contributing prominently to this broadening. The patterns of waveform changes can provide theoretical support for the restoration of information carried by radar echoes and microwave communications.