Low-speed maglev train is suspended above the guideway by the electromagnetic force. Compared with the wheel train, the maglev train has the advantage of low noise, small turning radius and advanced climbing capacity. The system stability problem in the condition of output saturation was studied to avoid instability phenomenon caused by network voltage constraints so as to improve the reliability of the system. A single-point levitation system model of the maglev train was established and a stable levitation control algorithm was designed. Based on the analysis of the output saturation element of the levitation controller, a maximal ellipsoid searching optimization method was presented for controller parameters design. Parameter optimization is achieved without changing the design of the control algorithm. Simulation and experimental results show that the optimized controller can get better control results, which can be used for the guidance of practical system operation.