The invention discloses a clamping device for a gas inflation type discharge capillary. The clamping device comprises a support base, a support frame, a copper electrode, a clamping sleeve, a seal ring, an extrusion pipe sleeve, a seal pipe sleeve, a threaded steel sleeve, a wire, a rubber pad and screws. The clamping device has the characteristics of simple and compact structure, convenience in operation, good clamping stability, stable gas inflation and discharge, and excellent airtightness, the clamping device can be used repeatedly, and the capillary is changed conveniently. The clamping device is applied to the field of interaction of laser plasma on the basis of the gas inflation type discharge capillary, and particularly applied to acceleration of electrons in a laser wake-field.