Abstract: A calibration has been carried out on neutron detection efficiency of bubble detectors prepared by China Institute of Atomic Energy at the tandem accelerator 2×1.7 MV by monoe nergetic neutrons of 20 keV～19 MeV from 7 Li(p,n) 7Be, T(p,n) 3He, D(d,n) 3He and T(d,n) 4He reactions. It shows that the bubble detectors have a threshold energy～100 keV. The detection efficiency increases steeply to three order of magnitude at the threshold. The detection efficiency above the threshold is nearly flat with value～1.5×10 -4. The bubble detectors can be used to measure neutron energy spectrum and as neutron dosimeter.