In this paper, the far-field body wave radiation of the fault which contains a asperity is studied by using dislocation model. Assuming that the ratio of the asperity size to the size of whole dislocation surface is C. and the fracture begins in the center, it calculates the effect of different C-values on the far-field seismic wave spectrum. The results show that comparing with the far-field amplitude spectrum of even penny-shaped fault because of the existence of asperity, it, is different that it causes the splitting of beginning part of wave spectrum in the first wave base when the fracture propagates to the fringe of the asperity. It is obvious that the asperity size effects on the amplitude spectrum. In addition, comparing P-wave spectrum with S-wave spectrum, it is found that the corner frequency of P-wave is higher than that of S-wave.