Experimental method to measure the prompt neutron spectra of ²³⁸U fission induced by fast neutrons has been developed at HI-13 Tandem Van de Graaff Accelerator Laboratory of CIAE. These techniques employ a multi-segment fission chamber and two liquid scintillator neutron detectors. TOF (time of flight) techniques are used for primary neutrons to select the fission events induced by monoenergetic neutron from ²H(d, n) reactions instead of breakup neutrons from ²H(d, np) reactions. The fission neutron TOF spectra are measured in coincidence with the fission fragments to distinguish fission neutrons from other secondary neutrons. The method permits measurements to a fairly good accuracy under large neutron and gamma ray background. The techniques are described and experimental spectra are presented.