Abstract: The physical model formula of gate capacitance considering quantum effect is derived by the band structure relationship based on the principle of microscopic physical properties of FinFET gate capacitance structure which is constructed by TCAD. And the characteristic curve of gate capacitance with gate voltage is simulated by MATLAB. Compared with the ideal state, the quantum effect in the inverse state will increase the gate capacitance, and the quantum capacitance becomes the dominant factor affecting the gate capacitance. At the same time, the factors determining the gate capacitance under different states are analyzed, and the characteristic curves of different fitting parameters are simulated in order to provide theoretical basis for improving the linearity of transistor's gate capacitance. The proposed gate capacitance model has practical significance for circuit design based on FinFET structure.