In order to achieve pressure surveillance in multi-sensitivity state

a kind of variable sensitivity pressure sensing probe is designed using fiber Bragg grating（ FBG）. Bare grating is fixed between center of thin film sheet and the lower housing. Pressure from surface of sensor probe is transmitted through film sheet to bare grating

and the size of the film sheet is changed by sensitivity switching valve so as to change sensitivity of sensor.Finite element simulation optimization calculation on film sheet is carried out

results in its deformation characteristics. Thickness of the film sheet is 1mm

and working radius is adjusted to 10 cm

9 cm and 8 cm

the maximum deformation occurs at the center of the film sheet under the 0. 1 MPa surface pressure

and the deformation at the center of the film sheet is 3. 875 mm

2. 561 mm and 1. 579 mm. After the bare grating is fixed

corresponding sensitivities are 38. 44 mm / MPa

25. 62 mm / Mpa and 15. 79 mm / MPa

so sensitivity transformation is achieved.