To research the uniform axial tension effect of an Electroless plating Ni-P coated Fiber Bragg Grating (ENFBG), the stress and strain properties of the ENFBG were analyzed based on its axial symmetry.The finite element method was used for theoretical calculations, then it was verified by following experiments. Theoretical calculation shows that under uniform axial tension, the core of the ENFBG is drawn uniformly, the shearing strain is far less than normal strain and can be omitted.The normal strain is proportional to the axial tension,and the change of center wavelength of ENFBG is proportional to that of the tension too. However, because of the difference of mechanic parameters between electroless plating Ni-P coating and optical fiber, the metal coating reduces the uniform axial tension sensitivity of the FBG. In sensor experiment, when the thickness of the coating is 7.25 μm, the sensitivity is 12.45 pm/MPa, R-square is 0.999 6,and the theoretical calculation value is 12.744 pm/MPa. Moreover, the sensitivity is decreased with the increase of the thickness of metal coating. The ENFBG is an excellent uniform axial tension sensor,because its center wavelength shows high linearity to uniform axial tension and its metal coating can provide good protection.