Constructing the Symmetrical Structural One-dimensional Photonic Crystal in the form of （AB）N1（BA）N2.By using the transfer matrix method,the relations between the optical properties of this one-dimensional photonic bandgap structure with positive-negative index alternant multilayer and its parameters are analyzed.The results show that the photonic crystals with positivenegative index alternant multilayer have wider photonic band-gap which is different from the case of traditional photonic crystals with narrow transmission bands when the two layers have the same optical thickness.There are extremely narrow transmission peaks in the main photonic band-gap.Numerical investigation shows that the structure investigated can be served as a super narrow pass band optical filter.The 3dB pass band obtained can be less than 0.000001nm near the infrared 1550nm,and the optical transmission in the pass band is almost 100%.This kind of photonic crystal super narrow band optical filter may find applications in super dense wavelength division multiplexing (SDWDM）for optical communication system.