In the cases of one-photon resonance and complete non-resonance, the effects of the relative carrier-envelope phase(RCEP) φ on pulse form and spectra characteristics of two-color ultrashort laser pulses in a Ξ-type three-level atomic medium are investigated by using numerical simulation.The results show that in the single-photon resonance case the RCEP has evident control role of profile and spectral characteristic of the two-color pulses.The RCEP can decide the amplitude, propagating velocity,p...