Abstract: By developing the vacuum multi-optical path switching component, the Y-type vacuum comparison channel and detector vacuum chamber were combined. A rapid switching of laser, ultraviolet continuous tunable monochromatic light and vacuum ultraviolet monochromatic light was realized with ultra-high vacuum environment guaranteed. Utilizing a cryogenic radiometer as the measurement datum and a UV-enhanced silicon trap detector as the transfer standard, the absolute spectral responsivity of UV detectors from 115 nm to 400 nm were measured. Experimental results show an absolute spectal responsivity measurement uncertainty of 0.8%～1.5% (k=2) from 115 nm to 230 nm, and 0.5%～1.0% (k=2) from 230 nm to 400 nm.