A type of one-dimensional photonic crystal (PC) with traditional medium (refractive index n1>0) and active medium (refractive index n2=n0－ki) alternant multilayer is designed. Its transmission spectrum is studied by transfer-matrix method.Simulation results show that it has two narrow transmission bands amplified whose half-width values are both about 0.6 nm with n1=1.45 and n2=3.8－0.10i, and the corresponding central wavelengths are only up to the thickness of the medium. An M×N matrix filter with gain is designed using M×N PC units with different thickness. The affection of thickness and refractive index of the mediums on the channels of this filter is investigated.The results reveal that the spacing and transmittivity of the channels,which are located in region of visible and infrared light, could be adjusted by changing the parameters of mediums.This will help the needed filter design.