Abstract: In order to simulate the transient process of the debris bed relocation behavior of sodium-cooled fast reactor (SFR), a large number of debris bed relocation experiments were carried out by bottom gas-injection method to study the effects of the experimental factors, such as particle properties, gas flow rate, gas injection location and horizontal flow rate, on the debris bed relocation behavior. In general, the larger gas-injection flow rate, the larger horizontal flow rate and the concentrated gas-injection near the center can promote the relocation of the debris bed. While the larger particle size, the irregular particle shape, the larger particle density and the smooth particle surface can hinder the relocation of the debris bed. The relocation characteristics of the mixed size particles are between the uniform size particles we used for mixing.