The invention relates to a lithium niobate crystal pressure sensor based on polarization interference, and belongs to the technical field of pressure detection. The lithium niobate crystal pressure sensor comprises a single-wavelength light source, and further comprises a polarizer, an LN crystal, a polarization analyzer and an optical power meter which are successively connected, and during pressure detection, the LN crystal is arranged in a pressure contact detection area. According to the lithium niobate crystal pressure sensor based on polarization interference, preparation is easy, the pressure is measured through a photoelastic effect, thus, the property of a force applying object cannot be changed, and detection results are more accurate; and the pressure detection process is completely based on the birefringence characteristic of the crystal and an interference effect, no current is generated, therefore zero power consumption is achieved, and energy saving and environmental protection are achieved.