The effect of minor additive Si or Ti, as well as both Si and Ti on behavior of radiation swelling for 316 stainless steel alloy (316 SS), irradiated at 550℃, using high voltage electron microscope (HVEM) with 1MeV electron beam was studied, and the swelling morphology was observed in situ under HVEM. Silicon (1 wt%), as well as Ti (0.1 wt%) can inhibit radiation swelling when the dose is not more than 11dpa. The 316 SS bearing 1 wt% Si additive has even larger swelling rate than that of the alloy without any additive, when dose is more than 13 dpa. 0.5 wt% Ti additive can even completely prevent it from swelling under the dose up to 33 dpa, but there are some small Ti compound particles segregated on radiation area. Experimental results show that the synergistic effect of both Si and Ti can completely prevent 316 alloys from swelling under radiation dose up to 33 dpa, but there are also a little Ti compound particles segregated on the circle of central area, but the number and size of the particles increase slightly with the dose.