An experimental facility designed for the calibration of silicon trap detectors against a laser-based cryogenic radiometer at three laser wavelengths in the Ultraviolet (UV) region was described. The experimental results for the spatial nonuniformity and nonlinearity of the silicon trap detector were shown and discussed. The component uncertainties associated with the measurement of radiation power and spectral responsivity of silicon trap detectors were analyzed. As the secondary detector standards, the expanded uncertainty of the spectral responsivity at three UV laser lines 266, 325, 379 nm is 0.19%, 0.14%, 0.11%, respectivily. This can improve the calibration capability of UV band spectral radiance.