Through the picture of dressed states, this paper investigates the spontaneous emission spectrum from a microwavedriven three-level atom embedded in double-band photonic crystals. The physical dynamics of the phase dependent phenomenon are analysed by comparing two models ＇upper level coupling＇ and ＇lower level coupling＇. When the phase is changed from 0 to π, the variety of spontaneous emission spectra from either of the two models are inverse to each other, in which the relative height and width of the peaks are determined by the density of states in photonic crystals.
