Abstract: Since the deuterium (D₂) in CRDM can’t be recombined completely, the surface temperature of the ⁶⁰Co control rod is high when it is withdrawn, and it is required to evaluate the flammability of D₂ mixture gas. In this article, theoretical and test method were used to determine the surface temperature of the ⁶⁰Co control rod when it was withdrawn, the minimum flammability volume fraction and ignition temperature, respectively. The results show it is unlikely that the high surface temperature can be the potential for D₂ ignition.