This article proposed a method to improve the equivalent circuit model of gallium nitride high electron mobility transistors, utilizing channel resistance RL to improve the accuracy of the model.The mathematical correction method and direct extraction method are used to extract the parameters of various components in the small signal equivalent circuit and establish a small signal model. Based on this model, typical Pucel noise models and Pospieszalski models are used to model and simulate thermal noise at room temperature. By comparing the changes in model parameters before and after the improvement, the effectiveness and accuracy of the improved model were verified, which can be used to predict the noise performance of GaN HEMT devices. The results show that the improved model is more accurate than the traditional model, and the higher the gate bias or frequency, the greater the impact of RL on the model; Compared to traditional models, the improved model has a lower average value of the main noise figures, with a 1.7% reduction in the minimum noise coefficient NFmin and a 2.7% reduction in the equivalent noise resistance Rn, demonstrating good noise characteristics.