Abstract: A large plasma with size of 60 cm×60 cm×2 cm was produced by hollow cathode under different discharge pressure and electric current.Reflection wave，transmission wave and absorption capacity were measured and calculated when C-Band microwave irradiated toward plasma sheet at different frequency.The results of experiment and calculation displayed that the three interactions of reflection，transmission and absorption are existed altogether at the same time；with the increase of discharge current，reflection wave decreased while transmission wave enhanced；with the increase of discharge pressure，the energy of microwave absorbed by plasma strengthened；when the density and electron collision frequency of plasma coupled with the frequency of microwave，the energy of microwave absorbed by plasma was up to 40%.It could be deduced that large plasma sheet can be used as beam-switching tool under a lower discharge pressure and the propagation properties of microwave in plasma sheet can be changed by adjusting the discharge parameters of plasma.