A high sensitivity pressure sensing system with a fiber Bragg grating (FBG) using the transverse strain characteristic of a straight bourdon tube (SBT) is presented and demonstrated for the first time to our knowledge. The transverse strain of the SBT makes the FBG tensioned. The pressure can be determined by measuring the shift of the Bragg wavelength. The experimentally obtained results indicate that the shift of the Bragg wavelength changes linearly with the applied pressure and the sensitive coefficients of pressure are approximately 6.22x10-3MPa-1. This represents a sensitivity value approximately 9.66x10-3pm/Pa. The pressure sensing system shows little hysteresis error.