This paper introduces the homogeneity measurement method of dielectric material’s permittivity. According to the resonant perturbation and field analysis theory, a measurement model of double sections in a cylindrical cavity is established. A cylindrical cavity is designed at TM_0n0 to verify the feasibility of the measurement method and the measurement resolution. The measurement system that consists of vector network analyzer, computer, cylindrical cavity, and movement device is designed to realize the online and automatic measurement using the measurement software. Three typical samples are measured by using this system, whose measurement differences compared with the data from the manufacturer are less than 0.02, 0.04, and 0.15, respectively. These results are analyzed to prove the feasibility and effectiveness of the measurement system.