Left-handed meta-materials can be fabricated by combining electric resonators with magnetic resonators to realize simultaneously negative permeability and permittivity, so the design of magnetic resonators is of great importance in designing new types of left-handed meta-materials. Dealing with the design of magnetic resonators, the design principle of magnetic resonators is proposed. The structure of the magnetic resonator must be equivalent to a mirror-symmetrical single loop in order to eliminate the unwanted bi-anisotropy. Based on the design principle, a coupling-enhancement magnetic resonator structure is devised. The negative permeability of the structure is verified by experimental simulations. The results show that the permeability of the structure is negative in 8.9GHz~10GHz and that bi-anisotropy is eliminated effectively. Compared with the conventional magnetic resonator SRR, the proposed magnetic resonator is simple in structure and much easier in fabrication and analysis.