The invention provides a cap structure on an intelligent charging machine charging gun. The cap structure comprises a round sleeve member; the upper end and the lower end of the sleeve member are provided with an upper limiting boss and a lower limiting boss respectively; the lower limiting boss is provided with a guide groove communicating with an inner hole of the sleeve member; the inner wall of one side of the sleeve member is provided with an insertion groove penetrating the side wall of the other side of the sleeve member; a round end cap is arranged in the insertion groove of the sleevemember; a supporting lug is formed at the lower end of the end cap; the supporting lug penetrates the lower limiting boss and a hinge joint shaft is inserted in and fixed to the supporting lug; the two ends of the hinge joint shaft are hinged to a supporting base which is formed at the lower end face of the lower limiting boss on the front side and the rear side of the supporting lug; the rear end of the hinge joint shaft is exposed out of the supporting base and is sleeved with a torsional spring; one end of the torsional spring is fixed to the supporting base and the other end of the torsional spring is fixed to a shaft sleeve; the shaft sleeve is fixed to the hinge joint shaft in a sleeving manner; the supporting lug of the end cap is provided with a push block perpendicular to the supporting lug. The cap does not need to be taken down during charging, so that loss of the cap can be prevented and a charging gun head can be protected after charging is over.