An in-situ ultraviolet sterilizing system for an in-body catheter, comprising an ultraviolet light source, an ultraviolet light transmission channel, a light source-channel coupling interface and end fittings, where the ultraviolet light source is connected to one end of the ultraviolet light transmission channel through the light source-channel coupling interface, The end fittings are connected to the other end of the ultraviolet light transmission channel; the ultraviolet light transmission channel and the end fittings extend into the in-body catheter, and the light propagates along the longitudinal direction of the ultraviolet light transmission channel and irradiates into the lumen of the in-body catheter On the surface, the end fittings can reflect or scatter the ultraviolet rays propagating axially along the ultraviolet light transmission channel to the direction of the included angle; the inner wall of the main pipe can be sterilized in situ through the ultraviolet light transmission conduit, and the inner wall of the cross branch pipe can be sterilized through the end fittings Sterilize in situ. The present invention can conform to the shape of the in-body catheter, and has the characteristics of compactness, portability, instant use, and the advantages of high efficiency, energy saving, environmental protection and long service life.