Abstract: An oxidized low density lipoprotein sensing device for a gallium nitride process is a GaN HEMT device including: a gateless AlGaN/GaN sensing transistor device, a testing window, a source, a drain, two metal connecting wires and a passivation layer. The gateless AlGaN/GaN sensing transistor device has an epitaxial wafer structure including a GaN layer and an aluminum gallium nitride layer. The testing window is disposed on the epitaxial wafer structure. The metal connecting wire is disposed on a source and a drain. The passivation layer is covered onto a surface of the sensing device except the testing window. A built-in piezoelectric field is created by the properties of FET and the polarization effect of AlGaN/GaN to achieve the effect of sensing the level of oxidizing proteins in human body quickly, accurately and easily.