The research of absorbing materials has always been a frontier topic in the field of military stealth technology, and the ferrotetroxide magnetic materials are the focus of research at home and abroad. The establishment of large scale space dynamic absorbing stealth model has high practical value in the military field.In order to study the dynamic absorbing effect of Fe3O4 particles in the large-scale air, it calculates the electromagnetic loss of Fe3O4 particles of particle diameters of 0.25μm and 10.57nm when the incident electromagnetic wave’s frequency is in the range of 2~18GHz and the time-varying dynamic electromagnetic loss at 18GHz through numerical simulation in the large-scale air. The results show that when the incident electromagnetic wave’s frequency is in the range of 2~18GHz, the electromagnetic loss generated by the 10.57nm Fe3O4 particle dispersion space is 0.40W to 11.59W, and the time-varying dynamic electromagnetic loss is 11.381W to 11.559W at 18GHz; the incident electromagnetic wave’s frequency is in the range of 2~18GHz, the electromagnetic loss generated by the 0.25μm Fe3O4 particle dispersion space is 0.22W to 4.88W, and the time-varying dynamic electromagnetic loss is 4.812W to 4.899W. It is concluded that Fe3O4 particles have good absorbing effect and the absorbing performance of nano Fe3O4 particles is better than that of micron Fe3O4 particles.