Selective laser melting (SLM) provides a novel path to fabricate austenitic stainless steels used in the nuclear reactors. Meanwhile, obvious differences in the microstructures of materials present between SLM and conventional process, which causes a discrepancy in the helium (He) tolerance. In present work, an austenitic stainless steel (type 316L) manufactured through SLM was irradiated by He ions at 450 degrees C with the concentration approximately 0.8% and then characterized via multiple methods. Results showed the special microstructure containing cellular sub-grains and nano-oxide inclusions, which formed owing to the SLM process, still distributed in post-irradiated samples. A decrease in the bubbles density, swelling rate, and hardness change has also been observed compared with conventional stainless steel. The interfaces provided by the sub-grain boundaries and nano-oxide inclusions act as effective trap sites for helium bubbles, which contributed to the enhancement of helium tolerance.