Abstract: For RLC series circuit with nonlinear capacitance, first approximate solution of primary resonance of nonlinear vibration system is obtained with method of multiple scales for nonlinear oscillations. Primary resonance responses of RLC series circuit show jump and hysteresis. With increasing of electromotive force primary resonance amplitude and resonant region increase. With increasing of resistance primary resonance amplitude and resonant region decrease.

Key words: RLC circuit, nonlinear capacitance, multiple scales, primary resonance, nonlinear resonance