A proton recoil method for measuring D-T neutron energy spectra using polyethylene film and a Si（Au）surface barrier detector is presented. An iteration algorithm for unfolding the recoil proton energy spectrum to the neutron energy spectrum is investigated. The response matrices R of the polyethylene film at angles of 0o and45o were obtained by simulating the recoil proton energy spectra from mono-energetic neutrons using the MCNPX code. With an assumed D-T neutron spectrum, the recoil proton spectra from the polyethylene film at angles of 0oand 45owere also simulated using the MCNPX code. Based on the response matrices R and the simulated recoil proton spectra at 0oand 45o, the respective unfolded neutron spectra were obtained using the iteration algorithm,and compared with the assumed neutron spectrum. The results show that the iteration algorithm method can be applied to unfold the recoil proton energy spectrum to the neutron energy spectrum for D-T neutron energy spectra measurement using the recoil proton method.