Spectrum weighting function method with an NE213 scintillation detector has been applied to measurements of integral parameters such as tritium production rate from 7Li, in-system neutron integral flux and gamma-ray heating rate in fusion neutronics experiments. The NE213 scintillation detector can separate neutron and gamma-ray responses from each other, and those detector responses give energy information of both neutron and photon from recoil-proton and recoil-electron spectra, respectively. Connecting these energy responses with the energy responses of the nuclear parameters of interest such as 7Li(n,n′α)3T reaction cross section, step function response of neutron energy and mass energy absorption coefficiency of gamma-ray, the corresponding nuclear parameters are obtained indirectly. The conversion method from the raw response of the detecter is introduced by a spectrum weighting function.