Superconducting photonic crystals are artificial periodic structures composed of superconductors and dielectric structures. In this paper, the transfer matrix method(TMM) is used to study the transmittance of one-dimensional photonic crystals consisting of cryogenic superconductor and lossless dielectric for TM wave. It is shown that a stop band staring from zero frequency can be apparently observed, whose cutoff frequency is adjusted by varying the temperature and the magnetic field. However, because of the contribution of the normal conducting electrons (NCEs) , taking no account of external magnetic field, the width of the low frequency photonic band gap (PBG) is no longer influenced by the temperature of the superconductor. The cutoff frequency of PBG adjusted by the temperature and the external magnetic field with the contribution of NCEs are compared with those obtained by neglecting them. However, when superconductors are in a normal state, the low frequency PBG of photonic crystals disappears.