Abstract: Innate immunity is the first line of immune defense. Space environments play important roles in phagocytosis, oxidative burst capacity and cytokine production of innate immune cells, which will threaten astronauts’ health and safety. Recent advances in the investigations of the effects of spaceflight environments on innate immune cells, including monocytes/macrophages, neutrophils, nature killer cells and dendritic cells, are summarized in this paper.