A composite dielectric material doped with rare earth metal oxide and a manufacturing method thereof are provided. The composite dielectric material is doped with nano-crystalline rare metal oxide which is embedded in silicon dioxide glass matrix, and the composite dielectric material of the nano-crystalline rare metal oxide and the silicon dioxide glass matrix is synthesized by the manufacturing method using sol-gel route. The dielectric value of the glass composite dielectric material is greater than that of pure rare metal oxide or that of silicon dioxide. In presence of magnetic field, the dielectric value of the composite dielectric material is substantially enhanced compared with that of the composite dielectric material at zero field.