Measurements of power frequency electric field are necessary to understand electromagnetic environments and optimize the high voltage electrical equipment. For this purpose, a novel fiber Bragg grating (FBG) based on the all-fiber power-frequency electric-field sensor is proposed. The sensor head actually is an optical fiber cantilever beam with a FBG, on which the polyimide resin as the electric field induction medium is multiple-layer coated. When the fiber cantilever beam is put into the electric field, the polyimide coating will produce the dynamic polarization effect under the induction of power frequency electric field because of the dielectric properties of polyimide coating materials, which, in turn, induces the fiber cantilever beam to vibrate periodically through the action of the timevarying electric field force. As a result, the Bragg wavelength of FBG also is modulated. The maximum shift of the Bragg wavelength is proportional to the applied electric-field strength. For demodulation of the detection signal, a laser source is used and its operating wavelength at the edge of the FBG reflective spectrum is selected. Through this operation, the change of optical power reflected from the FBG can be monitored and the power-frequency electric field strength can be measured. The experimental investigations prove that the proposed sensing method for power frequency electric field measurements is feasible and the prototype of the sensor had very high detection sensitivity and good measurement accuracy in the 1 kV to 4 kV voltage range.