Nanochannels exist widely in nature. Accurate control of the water filling state inside nanochannels is essential for realizing their functional properties. It is important to develop universal and easy to operate methods to control water filling and emptying removal in nanochannels. In this study, we prove that external electric fields can adjust the water filling and emptying behavior in nanochannels by using all atom molecular dynamics simulations. When the electrostatic field strength exceeds 1.4 V nm^-1, nearly all water molecules inside the nanochannel can be removed. This behavior can be attributed to the fact that increased electric field strength enhances the repulsion between the channel wall and water molecules, breaks the hydrogen bond network of water molecules, reduces the adsorption stability of water molecules in the channel, and finally leads to the overall removal of internal water molecules. Under the same field strength, replacing the electrostatic field with an alternating electric field can drive water molecules to re-enter the nanochannel and restore the water-filled state within a certain frequency range. The water filling behavior changes with the electric field frequency. Specifically, the nanochannel is partially filled with water when the alternating field frequency is lower than 0.05 THz. A stable and high-density water filling state is formed in the channel when the frequency ranges from 0.05 THz to 18 THz. When the frequency is higher than 18 THz, the channel presents a low-density water filling state. Simulation results confirm that the water filling state in nanochannels is closely related to the dynamic change of hydrogen bond structures between water molecules. Low-frequency alternating electric fields produce weak disturbances on the arrangement of water molecules, help form stable hydrogen bond networks, and maintain the high-density water filling state. When the field frequency is close to the natural vibration frequency of water hydrogen bonds, the stable hydrogen bond structure is destroyed, the diffusion ability of water molecules is improved obviously, and part of the water molecules leave the channel, resulting in a low-density filling state. By adjusting the electrostatic field strength and alternating electric field frequency accurately, the water filling state of nanochannels can be efficiently controlled. This study provides a theoretical basis for the precise regulation of water filling characteristics in nanochannels.