Abstract: The neutron detection system based on ST-451 liquid scintillator detector and BF₃ proportional counters was arranged, the instrument precision of the neutron spectrometers was less than 2.42%, and the system was applied on neutron determination in the nuclear effect of acoustic cavitation (NEAC). And the neutron detection sensitivity formula of BF₃ proportional counter was derived. The detection sensitivities of the BF₃ detectors were calibrated by 2.45 MeV neutrons which were emitted from deuterium titanium target bombarded by deuterium ions of high-voltage accelerator. The sonofusion neutron signals were determined used the BF₃ proportional counters, and the effective neutron emissivity estimations were of about 7.0×10⁴ to 8.0×10⁵ s^-1.