This work described a well-organized empirical modelling approach of large-signal GaN HEMT equivalent circuit for high-power applications. All the stages involved in the extraction have been described in this paper, beginning with the determination of extrinsic elements, and finishing with the intrinsic ones. Nonlinear capacitances and resistances have been extracted and modelled for saturation region, sub-threshold region as well as the triode region. Only six parameters were used to make the new channel current model, which represented the unique working principles of HEMT. The self-heating effect, virtual gate formation and dispersion phenomena have been integrated in the channel current model. As, only DC and S-parameters data have been required, this model has reasonably simple to develop and use in CAD software. The nonlinear features of the device and the harmonic components have been properly predicted by the proposed model. Small-signal to large-signal excitation regions showed excellent agreements using ADS software.