Abstract: The second radiation field outside the vacuum tube caused by proton beam loss in high intensity heavy-ion accelerator facility (HIAF) with Monte Carlo method was calculated. The energy of proton beam is within 50 MeV to 12 GeV. The basic problems such as second particle yield, energy spectrum and angular distribution were also discussed. These results are beneficial to selecting the detector type and its location and determining its dynamic range for beam loss detector, as well as to building the beam loss monitor system. Furthermore, they are meaningful in some way for the radiation protection of accelerator.