Abstract: A structure and design method of the photonic crystal fiber (PCF) for liquid sensing was proposed. The fiber core region of the hexagonal PCF was designed as two elliptical ventages, which were filled with water and ethanol, respectively, and then the propagation characteristics of two PCF structures were compared. The full vector finite element method (FEM) was adopted to numerically analyze the birefringence, relative sensitivity, confinement loss and nonlinear coefficient of the designed PCF structure. And the parameters of the optical fiber were optimized, meanwhile the parameters of the fiber core elliptical structure were adjusted. The results show that when the ellipticity is 0.6, the relative sensitivity of the PCF2 filled with ethanol can reach to 72.506 7% at the wavelength of 1.55 nm, and the confinement loss can deduce to the magnitude of 10⁻⁸. The designed model can be used in sensing as well as bio-sensing research and their applications.