As a novel gaseous signal molecule, hydrogen gas exhibits selective antioxidant effect and anti-inflammatory effect. In the medical field, hydrogen gas was originally discovered to show the antitumor effect, thereafter hydrogen has shown therapeutic potential in more than 100 diseases, including ischemic stroke. Today, the high incidence and mortality of cancer, as well as the lack of effective means of cure of cancer, have imposed a heavy burden on the medical expenditure. Therefore, how to realize cancer prevention and prolongation of survival appears to be of greater importance, and hydrogen gas is expected to play an important role in this field. In this paper, a review of the research progress of hydrogen antitumor is presented, which contains the antitumor mechanism, synergistic and attenuated effects, combined therapy, clinical research, and hydrogen administration methods.