Abstract: On the basis of observed facts that disturbance of amplitude at LFobtained in mid and low latitudes related with activity of the planetary waves in high latitudes during the winter warming, a mechanism which can better explain the above observed phenomena is given. The planetary wave is a main reason in producing absorption variation of the radio wave at LF. The atmospheric ionization rate can be changed by the planetary wave through two ways, Therefore, the disturbances of the electron density in the lower ionosphere occur when there are planetary waves and lead to variation of absorption at LFradio wave band. As a result, we observed the amplitudese at LF changes with the planetary waves at high latitudes. In this paper. we give the computing formula and results.