The effect of barrier layer periodicity asymmetry on photonic crystal quantum well transmission spectrum is studied by transfer matrix method. The results show that when the periodicity asymmetry is 0, transmission peaks become sharper as the barrier layer periodicity increases, but the transmittance is constantly equal to 100%. When the barrier layer periodicity asymmetry is any nonzero constant，the transmittance is below 100%; while with the increase of barrier layer periodicity, the transmission peaks sharpen with a constant transmittance. The transmittance of transmission peaks decreases with the barrier layer periodicity asymmetry increasing, and the greater asymmetry is, the faster the transmittance decreases, and the faster the transmission peaks narrow. These properties can provide theoretical basis for construction, preparation and design of the photonic crystal model.