LiNbO3 film (LNO)/AlGaN/GaN heterostructure was fabricated epitaxially. The preferable C+ oriented domains in LNO film lead to the formation of the spontaneous ferroelectric polarization. As a result, the sheet electron concentration of the 2DEG (ns) decreased from 1.13×1013 cm-2 to 1.04×1013 cm-2 when a LNO film deposited on the AlGaN/GaN. The ns decreased nonlinearly with decreasing the temperature. Additionally, the electron mobility for the LNO/AlGaN/GaN heterostructure decreased greatly compared with that for AlGaN/GaN heterostructure, which was caused by the non-uniform domain structure in the LNO film. By external bias switching the ferroelectric polarization, the relative enhancement of the 2DEG, about 7.68×1011/cm2, could be accessible from capacitance-voltage measurement. These results indicated that ferroelectric films combined with AlGaN/GaN would hold promise for next-generation GaN-based memory devices.