Abstract: To obtain the impact of γ rays for the organic scintillation film detector (OSFD) in the field of pulsed fission neutron detection, the response of the OSFD to X or γ rays was studied with the Geant4 program. Combining with a semi-empirical scintillation efficiency function, the energy response function of the OSFD to γ rays was obtained. To verify the simulation result, the sensitivities of an OSFD employing 0.3 mm film to some discrete energy points were tested experimentally with ¹³⁷Cs(662 keV) and ⁶⁰Co (1.25 MeV) γ ray sources, as well as some discrete semi-monoenergetic X ray points (48 to 208 keV) of a standard narrow band X ray device. The research is instructive for the improvement of the detector structure, and the results are valuable for the application of the detector in measuring pulsed X rays with wide energy distribution.