In order to accurately describe the characteristics of Radio Frequency (RF) power amplifier with memory effect, a new dynamic X-parameter amplifier modeling method based on traditional dynamic X-parameter model was proposed by combining with long-term memory effect and short-term memory effect. The new model preserves static kernel function of X-parameter model. A nonlinear function of memory was extracted by using the two-memory path model to replace dynamic kernel function. A novel FeedBack (FB) structure was proposed in which the output signal is a bivariate of amplitude and frequency, and the time-varying frequency variable was introduced to simplify the dynamic kernel function as a two-dimensional kernel function. The power amplifier was designed and modeled by the MW6S010N transistors. Simulation results indicate that the new model can correctly represent the characteristics of power amplifier with the excitation of single-tone large signal and Code Division Multiple Access (CDMA) signal. The Normalized Mean Square Error (NMSE) of the proposed method was decreased by 8.0 dB, 6.3 dB and 2.5 dB, respectively, in comparison with static X-parameter model, traditional dynamic X-parameter model and FeedForward (FF) structure X-parameter model. It is proved that the proposed model can more accurately fit the characteristics of power amplifier with nonlinear memory effect.