By using the transfer matrix method, phase properties of the transmitted light were studied from one-dimensional photonic crystal coupled-defect structure with the form as (HL)kA(LH)k containing N defects. It is found that for k=0, the transmitted phase curve is nearly linear. While for k≥1, the transmitted phase curve is stepwise and changes drastically around each transmitted peak with the corresponding phase-shift π or so. When introducing nonlinear materials, slight change of refractive index will result in a perfect π-phase-transition. Moreover, the transmittance is near zero at the π-phase-transition, which is helpful to reduce the influence by the dynamic chirp. Such phase properties hold great promise in designing various phase devices. Based on these properties, the sensitive all-optical switch and logic gate devices were designed as examples.