In this paper, a microstrip sensor based on a complementary split ring resonator (CSRR)derived structure is proposed to characterize the permittivity and permeability of materials. By loading an etched meandered conductive ring and an interdigital capacitor structure, effective separation of the permittivity sensing area and permeability sensing area is realized, and the field strengths of the corresponding areas are improved. The relationship between the resonant response (resonant frequency and quality factor) of the sensor and the permittivity and permeability of the sample under test (SUT) is discussed, and the theoretical basis for measuring the material properties is given. By analyzing the measured resonant frequency and quality factor, the real and imaginary parts of the permittivity and permeability of the SUT can be determined. The sensor was fabricated on a Rogers 5880 substrate, and four standard dielectric and magnetodielectric (MD) samples were tested. The results show that the measured values of the real and imaginary parts of the permittivity and permeability are in good agreement with the reference data.