A novel flux concentrator surrounded by a resonator is proposed in this paper. A complementary single split ring resonator (single CSRR) is introduced for the flux concentrator, while the resonator surrounding the flux concentrator employs a third-order stepped-impedance hairpin resonator (SIR). High frequency structure simulation software ANSYS HFSSv.11 is used to simulate the proposed flux concentrator and resonator. Moreover, the single CSRR is analyzed theoretically. Simulation and theoretical results shows that the novel flux concentrator surrounded by a resonator introduces a single CSRR, which improves the flux focus effect of the concentrator significantly, and so enhances the performance of coupling between the RF SQUID and the flux concentrator (the coupling coefficient ksc is improved 2 times) and increases the effective area to 1.227 mm2.