Abstract: The prompt fission neutron spectrum of ²³⁸U sample was measured by homemade N-4 nuclear emulsion. Details like the experimental layout and conditions, the track data reading, processing and correction were described. Also the relation of energy-range for recoil protons in the N-4 nuclear emulsion was derived by Monte Carlo simulation and fitting method. The fission neutron spectrum of N-4 nuclear emulsion was obtained, and the spectrum was corrected. The experimental results were compared with those of Maxwell model. The results show that they are in good agreement within the range of uncertainty, and the availability of N-4 nuclear emulsion in the measurement of high-energy segment of the prompt fission neutron spectrum is proved.