Abstract: Extended binary phase shift keying(EBPSK) modulation is a high efficiency ultra narrow band(UNB) technology. To discuss further modulating mechanism, study of EBPSK power spectrum structure is necessary. In this paper, by means of spectral analysis on periodic signals, Fourier expansion on EBPSK average basic modulating waveform and relevant discussion, the time-domain component of linear power spectrum is obtained. Furthermore, the conclusion that both time-domain and frequency-domain component can be added is inferred. The modulating simulations testify these results. The work is conducive to the further EBPSK and other UNB modulation research.