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DC characteristics of AlN/β-Ga2 O3 high-electron-mobility-transistor (HEMT) was studied in this paper by using the device simulation software. Due to the strong polarization effect of AlN, a high concentration of two-dimensional electron gas (2DEG) is generated at the interface of AlN/β-Ga2 O3 heterojunction, resulting in AlN/β-Ga2 O3 heterojunction based HEMT exhibits superior device performance. Theoretical calculation shows that the surface charge density generated at the interface of AlN/β-Ga2 O3 heterojunction is 2. 75 ×1013 cm-2. By analyzing the energy band structure and channel electron concentration distribution of the device, the effects of parameters such as AlN barrier layer thickness, gate length, gate drain spacing, and metal work function on the transfer and output characteristics of the device were studied. The following results were obtained. As the thickness of AlN barrier layer increases, the threshold voltage decreases, the maximum transconductance decreases, and the drain saturation current increases with the increase of channel electron concentration. As the gate length shortens, the transconductance increases, and the gate length shortens to 0. 1 μm, the device experienced a short channel effect. And as the gate length decreases, the electron concentration in the channel area under the gate increases, while the electron velocity remains basically unchanged, resulting in an increase in drain saturation current, a decrease in conduction resistance, and a deterioration in the saturation characteristics of the device. As the distance between the gate and drain increases, the transconductance increases, and the electron concentration in the channel region remains unchanged, while the electron velocity slightly increases, resulting in an increase in saturated leakage current. An increase in the Schottky gate metal work function will increase the threshold voltage without changing the device transconductance. The decrease in channel electron concentration will lead to a decrease in drain saturation current. The above conclusions provide a theoretical basis for the optimization and improvement of subsequent devices. [ABSTRACT FROM AUTHOR]