In order to improve the sensitivity of a pressure sensor, a novel pressure sensing structure of photonic crystal fiber with side hole and high birefringence was designed, based on the theory of photonic crystal fiber and its high birefringence and flexible design structure. The force and mode field distribution of sensing structure were simulated and analyzed by using full vector finite element method and COMSOL software. The dependence of pressure sensing characteristics on geometrical structure and free space wavelength was obtained. The optimum structural parameters were obtained by optimum design. The high pressure sensitivity was further obtained. The results show that, under the optimal structure, when free space wavelength is 1.55μm and pressure is 200MPa, polarization phase sensitivity is 166.2rad/(MPa·m) and maximum pressure that can be applied is 720MPa. The sensitivity of phase mode birefringence is maintained at about 4.1×10-5MPa-1. The research is helpful to improve the sensitivity of pressure sensors.