Current collapse in AlGaN/GaN high-electron-mobility transistors was studied and the effect of effective external electrical field on the concentration of two-dimensional electron gas (2DEG) near the channel of hetero-junction of AlGaN/GaN was simulated through the self-consistent implementation of the one-dimensional Poisson-Schrdinger equations. An inverse piezoelectric polarization model was proposed to analyze the degradation of 2DEG and the current collapse. It was found that the density of 2DEG was strongly dependent on the inverse polarization. When the voltage was 0,10 and 15 V, the density was 1.53×1013cm-2, 1.04×1013cm-2 and 0.789×1013cm-2, respectively. It was clear that the 2DEG density dropped 48.4% with voltage increasing from 0 to 15V when the inverse piezoelectric polarization was considered. At last, the method of restraining current collapse was further discussed.