A new calculation method of nonlinear oscillation circuit is presented and called as the response frequency alternation method. The phase angle is introduced as the independent functions. The waveform functional of the nonlinear oscillation circuit is shown as the cosine functional of the independent functions. The first derivative of the independent functions about the independent variable is meant by the response frequency of the circuit. The solution of the nonlinear state equation for the circuit is summed the determining of the response frequency for the circuit

and computed it with the alternation method. Using the differential relation of the response frequency between the phase angles

the approximate expression of the inverse transform for the independent variable is computed

and the expression of the variation for the state variable of the nonlinear oscillation circuit following with the time is shown as the parameter form of the independent functions. It is broken through the limit of the excitation parameters much less than 1 (i.e. weakly nonlinear) of the perturbation method and suitable for the strongly and weakly nonlinear circuit. A three-electrode oscillation circuit is discussed specifically with the excitation parameters of the 0.8 and 1

the calculation results are in good agreement with the numerical integral method after two times of iterative frequency

but the perturbation method is invalid.