In order to achieve the superior filtering characteristics of one-dimensional photonic crystal, the gradient refractive index defect layer is introduced, which can suppress electromagnetic wave of certain frequency and generate the photonic band gap. The finite difference time domain (FDTD) method is used to solve Maxwell equations. The corresponding transmission spectrum lines are studied when the refractive index of defect layer is parabolic. Influences of the refractive index ratio, thickness ratio and cycle number of periodic dielectric layer on the filtering characteristics are analyzed. Results show that a wider filter bandwidth of one-dimensional photonic crystal with gradient refractive index defect layer can be realized by increasing the refractive index ratio. The transmission peak position is affected by changing thickness ratio, and the transmittance is affected by changing the periodic number. Research results have a certain reference value for improving the performance of photonic crystal filters.