Abstract: To design high-quality optical filter device, the modulation of medium refractive indexes in barrier and well layer on filter bandwidth of optical quantum well was studied with transfer matrix theory and computational simulation method. The results show that the filter bandwidth is responsive to the refractive indexes of both barrier layer and well layer; filter bandwidth narrows down as the refractive index of high-refractive medium in barrier layer increased; and the greater ratio between refractive index sums of barrier layer and well layer, the narrower filter bandwidth of optical crystal quantum well becomes. The response mechanism of optical crystal quantum well filter bandwidth to medium refractive index can provide theoretical basis to improve the quality and performance of optical filter device and also has positive effects on the theoretical study of optical quantum well.