A resonant power circuit, a magnetic resonance imaging system, and a transformer are provided. The resonant power circuit is disposed within a scan room of a magnetic resonance imaging system, and is used for supplying power to a switch device in a radio-frequency amplifier of the magnetic resonance imaging system. The resonant power circuit includes: an inverter circuit, a resonant transformer circuit, and a rectifier circuit. The ratio of a resonant frequency is greater than 1 and less than a first threshold, a series resonant frequency being determined according to a resonant capacitor and a resonant inductor.