An inverter control circuit with a resonant frequency modulation function provides a control circuit module that can modulate different resonant frequencies externally to fit loads of different modes without changing the inverter components such as a voltage transformer or redesigning the circuit layout. The RC oscillation circuit of a resonant frequency controller of the invention includes several separate resistors, and the separate resistors of the RC oscillation circuit are coupled to at least one switcher to form an open circuit or a closed circuit to determine the total resistance of the RC oscillation circuit for modulating different resonant frequencies.