Productions of transmute elements (hydrogen and helium) have great influences on the resistance to irradiation damage in structural materials for fusion reactor. The evolution of irradiation damage in bcc iron is investigated with ion implantation and electron irradiation. Pure iron implanted by He+ or D+ ions at room temperature are aged at 500℃ for 1 h, then irradiated by electrons under high voltage electron microscope. The results show that interstitial loops (i-loop) and vacancy loops (v-loop) are formed in He+-implanted iron and D+-implanted iron respectively. Under electron irradiation, due to the absorption of interstitials atom, i-loop grows up while v-loop shrinks. According to the rate of variation of dislocation loop, v-loop absorbs more interstitial atoms, i.e., the dislocation bias of D+-implanted iron is larger than that of He+-implanted iron, which means that the v-loop has the more contributions to irradiation swelling than i-loop. The causes of the different natures of dislocation loops formed in D+-implanted iron and He+-implanted iron are analyzed by the structures of He-V and D-V complexes.