This paper presents a method for obtaining the dispersion relation of the refractive index near the direct band-gap of GaAs/GaAlAs multiple quantum wells (MQW) materials. Its characteristic is introducing room temperature excitonic oscillating factors into the dielectric coefficients on the basis of dealing MQW with optical transmit matrixes on the system of multi-layer media films, then to fit the curve of experimental reflection spectrum of the sample. This dispersion relation is very important to the design of optoelectronic elements and their theoretical expectations. By this way, we can obtain not only the dispersion relation of the real and imaginary part of the refractive index, but also the resonant excitonic absorption spectrum.