[en] Using a method combining experimental measurement and Monte Carlo calculation, the measurement technique of high-threshold detectors is more systematically studied in special experimental conditions of small measurement inter-space and weak neutron flux. Influenced factors mostly include self-absorption of γ-ray in foils, self-shielding of neutrons, perturbation among detectors and scattered background neutrons and so on. the varied rules as function of a foil's thickness are attained. The study's results show that when the thickness of a foil is suited, the experimental systematical errors may fall down. The experimental-shielding method is used to proof-test the fraction of scattered back-ground neutrons, and for high-threshold detectors, the influence of background neutrons is very small. (authors)