Modulation of activated impurity on filter property of double barrier photonic crystal quantum well is studied by computational simulation method. The results show that no matter which layer the activated impurity is doped in, there appears light gain amplification (with different maximum values) and bandwidth narrowing (with constant minimum values) in filter channels of quantum well. With different sensitive responses in different channels, response of magnification and bandwidth to impurity in inner-barrier layer is more sensitive than the one in outer-barrier layer; similarly, the response to single-layer medium is more sensitive than the one to multilayer. When there is activated impurity in well layer, sensitivities of channel in center well responding to impurity in single-layer and in multilayer medium are the same, but the response sensitivity of shortwave channel to impurity in multilayer is more sensitive than that in single-layer medium. Inversely in long wave channel, no matter which layer activated impurity is doped in, the response sensitivities remain an equivalent extreme value. These properties provide positive guidance for design of photonic crystals with narrow bandwidths, high-quality optical filtering and high-multiples optical amplifiers.