The transmission spectra of one-dimensional photonic crystal (ABCBA)m are calculated by means of the transfer matrix method. As the dielectric constant is a real number, the transmission resonance spectrum in photonic crystals is of multi-channel optical filtering properties. When the C medium is added with active matter, there is only one resonance peak. If the number of m is an odd, the rate of transmission is 0.05 at ω/ω0. If the number of m is even, then the rate is up to 104. The strength of the gain is closely related to the number of m and the value of the imaginary part. It provides theoretical guidance for designing new photonic instrument with properties of single-channel optical filter, multi-channel optical amplifiers and filters.