An absolute calibration setup for laser-induced breakdown spectroscopy detection system is built based on the radiometry theory. A tungsten halogen lamp equipped with an ultraviolet glass filter and a fused silica diffuser is used as standard light source for the calibration. Absolute calibration of a laser-induced breakdown spectroscopy detection system with a Czerny-Turner spectrometer in the ultraviolet range is performed. The absolute spectral response of the system in the range of 310~385 nm is obtained with an uncertainty less than 7% by 2 standard deviation estimate. The absolute spectral calibration provides a way to evaluate the hardware of the laser-induced breakdown spectroscopy detection system.