The behavior of bubble-loop complexes formed in reduced activation ferritic/martensitic (RAFM) steels under He⁺ irradiation at elevated temperatures was investigated by transmission electron microscope (TEM), and corresponding simulations on the interaction between He bubbles and dislocation loops were also carried out by molecular dynamics (MD). China Low Activation Martensitic (CLAM) steels were irradiated under18 keV He⁺ with the fluence of 1 × 10²⁰ ion/m² at room temperature, 250 °C, 350 °C, 400 °C, 450 °C and 550 °C, respectively. Bubble-loop complexes were observed in all specimens when irradiated at 250 °C and above. Almost all of He bubbles were located inside the dislocation loops when the irradiation temperature reached up to 550 °C. Moreover, the formation of the complexes was independent of the type of dislocation loops since both a₀ <100> and a₀/2 <111> loops could form bubble-loop complexes. He bubbles were situated to be more stable inside the dislocation loops than that in the matrix according to the experimental results. The MD simulations showed that the dislocation loop can be locked by the He bubble, which could elucidate the mechanism of the observed bubble-loop complexes formed in He irradiated RAFM steels. The mean size of dislocation loops decreased when irradiation temperature increased to 550 °C, which can be ascribed to the high emission rate of point defects from dislocation loops at high temperature.