The blue shark (Prionace glauca) is a main bycatch shark species in the tuna longline fishery. Based on the data of 778 blue sharks from 1272 fishing sets recorded by Chinese tuna longline observers in the Indian Ocean from 2012 to 2019, a generalized linear model (GLM) was applied to analyze the at-haulback mortality (i.e., the mortality rate when fish was captured and hauled back to the deck) and potential influencing factors of blue shark. The results were shown as follows:The overall at-haulback mortality of blue shark was 13.4%, and the at-haulback mortality of males was higher than that of females. Among the potential influencing variables, hook type, hook size, individual size, capture depth and capture latitude had significant influences on the survival status of blue sharks, and the impacts of hook type and capture latitude were the greatest. The interaction between hook type and latitude, as well as between gender and fork length also greatly contributed to at-haulback mortality. When using olecranon hooks, the more northerly being caught, the lower mortality rate was observed; for the other three hook types, the more northerly being caught, the higher mortality rate was observed. The larger the female blue shark was, the lower the mortality rate was observed; however, there was no clear pattern between the mortality rate of male blue shark and their individual size. This study can provide scientific information for reducing the estimated fishing mortality of blue shark and promoting the sustainable use of resources in this fishery.