The formyl radical(HCO)and its sister radical,isoformyl(HOC),have been considered as important reaction intermediates in combustion chemistry and interstellar molecule formation.Compared to the rich research background of HCO,the species HOC has received little attention.In this paper,the historical advances on the geometrical structure,electronic nature and stability of HOC radical at different calculation levels were summarized,providing new theoretical design ideas for its future characterization in experiment.