By using the transmission matrix, the activation effect of complex medium on the optical propagation properties of optical quantum well has been studied. The result shows that, the light transmissivity and internal local electric field of an optical quantum well can be activated by complex medium. There is always an internal local electric field in the optical quantum well made of whether real medium or complex medium. The local electric field will always cause the frequency quantization and the appearance of discrete narrow transmission peaks in the transmission spectrum. Active impurities are added to the medium A. When the imaginary part of dielectric constant of complex medium, namely k, is positive, both the local electric field in the optical quantum well and the transmissivity of discrete narrow transmission peaks will be attenuated. With the increase of k value, the monotonic attenuation of internal local electric field becomes more obvious. However, the sensitivity of the response of local electric field to the positive imaginary part k is different at different wavelengths of optical quantum well, and the electric field at the central wavelength of the quantum well is the most sensitive to the k value. When the imaginary part of dielectric constant of complex medium, is negative, both the local electric field in the optical quantum well and the transmissivity of discrete narrow transmission peaks will have an amplified gain. As the value of negative imaginary part |k| increases, the internal local electric field will increase to a maximal value and then become attenuated. However, the maximal value of the local electric field in gain amplification and the corresponding |k| value are different at different wavelengths of the quantum well. To be specific, the local electric field in the short-wave direction of the quantum well is the most sensitive to |k| value, while the local electric field in the long-wave direction is the least sensitive to |k| value. The modulation mechanism of complex medium towards the light transmission characteristics of optical quantum well has positive guiding significance for the theoretical research and practical design of new optical filters, optical amplifiers and optical holophotes, and for the research of internal mechanism of light transmission characteristics of an optical quantum well.