We have employed 10 digital records and computed the spectral magnitude and the seismic radiated energy for 18 large earthquakes (Ms≥6) occurred in Eur-asian belt during 1986–1989. The nine digital stations (CD-SN) distribute all over China and one in Germany. The spectral magnitudes of various period have different stability among stations. The stability is better for maximum spectral magnitudemi and seismic radiated energyE, their differences among stations are smaller, especially for the stations where the ray path main penetrates the low mantle. But the stability of corner period is usually not good. The relation between seismic radiated energy and seismic moment magnitudeMw is lg (E)=1.5Mw+c, wherec is a constant. The maximum spectral magnitudemi=Mw+0.1, it is consistant with theoretical prediction.