The influence of lateral pressure on the birefringent characteristics of high-birefringent microstructure fiber is theoretically investigated using a full-vector finite element method, which is different from other reports applying hydrostatic pressure. In the wavelength range 600～1700 nm, the results indicate that the variation of the phase and group modal birefringence is different, when the lateral pressure is applied along the slow axis and fast axis of the microstructure fiber, respectively. Furthermore, when the lateral pressure is applied along the slow axis and fast axis, respectively, the effect of lateral pressure on the sensitivity of phase and group modal birefringence of microstructure fiber is also different. The research has great signification in microstructure fiber designing, microstructure fiber sensors especially multidimensional optical fiber sensors.