Provided is an antibody or a fragment thereof, which can be specifically bound to an S3-4 ring of a voltage sensor paddle of a domain III of voltage-gated sodium channel Nav1.9 α sub-unit, and is able to inactivate a voltage sensor valve to keep sodium ions from entering nerve cells normally. Also provided is an epitope polypeptide specifically bound to the antibody or the fragment thereof, a pharmaceutical composition comprising the antibody or the fragment thereof, and a use of the antibody or the fragment thereof in preparing a drug for treating and diseases related to pains.
