The nematic liquid crystal (NLC) infiltrated photonic crystal fiber (PCF) used as a switch modulated by electric field is demonstrated. The switch consists of the infiltrated solid core PCF into which Bragg gratings are written. It is confirmed that the switch can achieve an accurate operation through measuring the reflected light with the change of electric field intensity from 1.4 kVrms/mm to 2.1 kVrms/mm. When the electric field intensity exceeds the threshold, the change of only 0.01 kVrms/mm can cause the wavelength shift of 1 nm. It is approved that the switch with such a structure provides a high sensitivity. The reflection peak is stabilized at about 15 dB which is high enough to separate from the factors such as system noise and error, and it can improve the control precision.