The hydrostatic pressure sensitivity of polymer optical fibre Bragg grating of different diameters is investigated. For this purpose Bragg gratings are inscribed in single-mode polymer fibre and also in etched single-mode polymer fibre. The inherent pressure sensitivity of the grating are experimentally investigated up-to 1MPa by monitoring the change in the reflected peak wavelengths due to pressure. It is observed that polymer FBGs exhibit a positive Bragg wavelength shift and is also more sensitive compared to silica FBGs. The pressure sensitivity of the polymer FBG can be increased by reducing the diameter of the fibre.