Defect modes are found inside the photonic gap with zero effective phase when mutiple periodic double defect layers of single-negative materials are added into the traditional one-dimensional photonic crystals. The results show that by varying the total thickness of the defect layers, the frequency interval of the defect modes is increased and the transmission of defect modes is decresed when the thickness of each defect layer is identical. When altering the thickness-proportion of the defect layers the frequency interval of the defect modes can be changed. If the general zero average permeability and permittivity conditions are both satisfied, twin defect modes are found to merge into each other. On the other hand, defect modes inside the zero-effective-phase gap are insensitive to incident angle. However a new angle gap emerges because of the change of the incident angle. The angle gap enlarges with the increasing of the incident angle but is unrelated with the thickness of the defect layers.