The invention discloses a triaxial cable connection component for a nuclear reactor ex-reactor nuclear detecting system, relates to the technical field of electric connection pieces and aims at solving the technical problem of electric signal transmission of the nuclear reactor ex-reactor nuclear detecting system. The triaxial cable connection component comprises a triaxial adapter and two triaxial connectors; each triaxial connector comprises a connector shielding housing, an outer layer shielding sleeve, a first ceramic insulator, an inner shielding sleeve, a second ceramic insulator and a connector pin; the outer layer shielding sleeve, the first ceramic insulator, the inner shielding sleeve, the second ceramic insulator and the connector pin are fixed in the connector shielding housing and are sequentially connected in series with one another; the triaxial adapter comprises an adapter shielding housing, an adapter insertion core, an adapter inner insulating layer, an adapter inner shielding layer and an adapter outer insulating layer; the adapter insertion core, the adapter inner insulating layer, the adapter inner shielding layer and the adapter outer insulating layer are fixed in the adapter shielding housing; a connection screw cap is arranged on each connector shielding housing in a sleeving manner; and outside threads are formed in each connector shielding housing. The triaxial cable connection component provided by the invention can work in a severe working environment in a reactor containment.