Abstract: Based on the assumption that the Cosmic Radio Noise is an isotropic backgrouna electromagnetic radiation, by use of the ray-optics method the expression of the scintillation power spectrum of electron density space fluctuation is obtained,which obeys the inverse power low of the ionospheric irregularities.Compared with that of Radiostar and satellite beacon scintillation.the ionospheric scintillation of cosmic radio noise reduces the number of variables,the variable introduced by relative movement no longer exist.The effect of the structure parameters L_y、l_y、p、η, on the power spectrum is also studied using numerical simulation. As a result, it is found that more than 60% of the irregular strutures associated with the data recorded by Riometer during the period of the ionospheric absorption events have L_y> √λZ and 0.2<η <0.5.