In order to improve the radiation efficiency of the electrically small antenna, a three-layer miniaturized loop antenna based on split resonance ring structure is proposed. The antenna consists of a feeding layer and two coupling layers and is excited by electromagnetic coupling. An E-shaped matching network is designed in the feeding layer to reduce the reverse current, which is the shortcoming of traditional coupling feeder SRR antenna. The coupling ring structure is used to realize strong magnetic coupling and reduce the metal loss. A fixed air gap between the coupling layer and the feeding layer is introduced to effectively reduce the dielectric loss and improve the radiation efficiency. The influence of dielectric substrate on the antenna performances is analyzed by electromagnetic simulation. The proposed antenna is fabricated and measured. The experiment shows that the measured results are basically consistent with the simulated results. The center frequency of the antenna is 50.03 MHz, and the electrical size is 0.045λ0×0.045λ0×0.01λ0 (λ0 is the working wavelength). The antenna has good omnidirectional performance in the horizontal plane, and the radiation efficiency is more than 41%.