The experimental technique for measurement of (n, xn) double differential cross sections for incident neutron energy above 100 MeV has been attempted to be developed with continuous-energy neutrons up to 400 MeV. Neutrons were produced in the spallation reaction by the 800 MeV proton beam, which was incident on a thick, heavily shielded tungsten target at the WNR facility at Los Alamos National Laboratory. The energies of incident neutrons were determined by the time-of-flight method. Emitted neutrons were detected by the recoil proton method. A phoswich detector consisting of NaI(Tl) and NE102A plastic scintillators was used for detecting recoil protons. We compared the preliminary experimental cross section data with the calculations by PHITS and QMD codes.