By using the transfer matrix,the band structures,defect mode and field propagation characteristics of one-dimensional photonic crystals composed of single-negative (SNG) material are studied. It is shown that this structure possesses a new type of photonic gap which is insensitive to the incident angle and the light polarizations,as well the change of scale length. When a normal dielectric defect layer is inserted,the defect mode is insensitive to the angle of incidence,but the electro-magnetic field in the defect layer is strongly localized,and the number of the defect modes increases with the thickness of the defect layer. By using the transfer matrix, the band structures, defect mode and field propagation characteristics of one-dimensional photonic crystals composed of single-negative (SNG) material are studied. It shows shown that this structure possesses a new type of photonic gap which is insensitive When the incident angle and the light polarizations, as well the change of scale length is as well as when the normal dielectric defect layer is inserted, the defect mode is insensitive to the angle of incidence, but the electro-magnetic field in the defect layer is strongly localized , and the number of the defect modes increases with the thickness of the defect layer.