[en] In order to calibrate the sensitivity of the scintillating-film neutron detector with the scintillator thickness great than 0.1 mm in 5SDH-2 accelerator at the Radiation Metrology Center of China Institute of Atomic Energy, a neutron shield was designed by modeling and optimizing with MCNP program. Experiment results show that this shield can attenuate the neutron fluence out of collimator to one-tenth of that in the collimator, and constrain the background signal to the level of photomultiplier's (PMT) dark current, therefore, it can make signal-to-noise of the detector great than 1:1 for the detector with thickness of scintllator above 0.1 mm. Calculation results indicate that sensitivity change resulted from collimator scattering is less than 5%. (authors)