To address the problems of large volume, inconvenient to directly measure the real electromagnetic gap of traditional eddy current sensors, a method of levitation gap detection for maglev train based on electromagnet with a composite coil is proposed. Firstly, the equivalent electromagnetic gap detection principle for the levitation system is analyzed, and the equivalent impedance model of the composite coil is formulated for the coupling effect of electromagnet and high-frequency eddy currents in the surface of the F-rail on the magnetic field of the composite coil. Secondly, the excitation frequency and the structure of the levitation system based on the gap detection of the composite coil are optimized through finite element simulation to improve the detection sensitivity. The resonant detection circuit and signal demodulation circuit are designed to effectively suppress the crosstalk between the levitation system and the gap detection system. Finally, the static performance test and levitation experiment are carried out, the linearity is 0. 4% after correction, the maximum fluctuation peak-to-peak value of the static output is 89μm at constant gaps, the suspension system is capable of stabilizing the suspension under different operating conditions for a given gap, step disturbance and offset disturbance. The experimental results show that the response speed and detection error of gap detection meet the system requirements.