The invention discloses a transient ultraviolet multispectral radiometer, comprising a plug-pull type aiming lens, a guide rail component, a cassegrain imaging system, an ultraviolet spectrograph, a CCD driving circuit, a high-speed collection storage system and a computer which is provided with a spectrum measure data processing soft package. The cassegrain imaging system aims at a light source to be detected with the help of the aiming lens, adjusts self-focal distance and makes the light source to be detected for imaging clearly on the incidence slit of the ultraviolet spectrograph; the output optical signal of the ultraviolet spectrograph is converted to an electrical signal through the CCD driving circuit and is collected and stored by the high-speed system, and then is transmitted to the computer by a USB line. The spectrum measure data processing soft package calculates the spectrum power curve, the peak value wavelength, the corresponding power value of the light source to be detected according to relevant calculation means. The invention not only can detect the ultraviolet spectrum of the microsecond transient line light source and the transient side light source during single flashing time, but also can detect the ultraviolet spectrum of the steady state radiation light source including weak energy or the far radiation light source, and has good application prospect.