TiO2 films deposited on GaN layers at room temperature through a simple and low-cost liquid-phase deposition (LPI)) method are investigated. The deposition rate is 70nm/hr. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) are used to analyze chemical composition. Upon annealing under an atmosphere of high purity N2, the crystalline phase of TiO2 is transformed from the amorphous to the anatase and rutile phases. Electrical characteristics show the leakage current is about 1.01×10-7A/cm2 at 1MV/cm, and the breakdown field is more than 6.5MV/cm. Moreover, the dielectric constant is about 24.4, and D it can be 7.48 × 1011 cm-2eV-1 from C-V measurement. AlGaN/GaN MOSHEMTs with TiO2 gate dielectric and HEMTs are also fabricated for comparison.