A method for thermal neutron flux measurement by γ spectrometer is introduced. The 411keV γ ray peak areas for both Au and Eu foils irradiated in a reference field were first measured by a γ-spectrometer. And the absolute neutron flux for the Au foil was determined by a 4πβ-γ counter Then the neutron flux corresponding to

152

Eu can be derived from the 152Eu to

198

Au peak area ratio and the above-mentioned absolute neutron flux for Au. For an unknown field

the 411keV peak area of an irradiated Au foil in the field was measured by another γ-spectrometer

which also measured the peak area of the 411keV γ rays from the

152

Eu foil irradiated in the reference field. Based on the ratio of these two peak areas and the aforsaid neutron flux for Eu in the reference field

the absolute neutron fiux of the unknown field could be determined.