The defect modes in one-dimensional photonic crystals containing defect layers of multiple single-negative materials are analyzed. The photonic crytals are stacked alternately with single-negative-permittvity and single-negative-permeability media with periodic defect layers. Twin defect modes are found inside the photonic gap with zero effective phase. By varying the defect number or the thicknesses of the defect layers, the frequency interval of the defect modes can be changed, but the number of the defect modes remains two. The two defect modes inside the zero-effective-phase gap are insensitive to incident angle;the normalized frequency shift of the defect modes is always less than 0.03 as the incident angle varies. Moveover, the electric fields at the frequencies of the defect modes are strongly localized at the interfaces between defect layers and periodic structures.