Abstract: The benchmark experiment is one of the important experiment methods for verifying the nuclear data. Liquid scintillator detector is the main detector used in the neutron nuclear data benchmark experiments, and the accuracy of the experiment results is affected by the precision of the detection efficiency of the detector directly. Using time-of-flight method and a ²⁵²Cf neutron source, the neutron relative detection efficiency curve of the liquid scintillator was measured in 2.0-10.0 MeV energy region. And the absolute detection efficiency of mono-energetic neutrons was also measured at 2.9 MeV with the time-of-flight method and the d-D reaction neutron source. After normalizing the relative detection efficiency curve to the absolute detection efficiency at 2.9 MeV, the absolute detection efficiency curve in this energy region was obtained. The calibrated detection efficiency of the liquid scintillator was also compared with the calculation result of the Monte-Carlo code NEFF, and good agreement was obtained.