Movable contactless power supply (MCPS) is superior to traditional contacting power rails for the high-speed maglev trains. The resonant converter is normally preferred so as to improve the power efficiency of MCPS. But this MCPS is characterized with variable load parameters. This paper analyzes the characteristics of resonant converter with frequency and system delay. A direct resonant frequency tracking algorithm is developed to get the resonant current frequency and compensate the system delay, which could minimize switching losses and device stress. The validity of algorithm is verified by simulation results used to MCPS of high-speed maglev trains.