Graphene-base material is a potential candidate of nano-additives for improving the performance of energetic materials. We employed ReaxFF-lg reactive molecular dynamics to investigate the effect of different 2D nanocarbon materials (such as graphene and graphyne) in the thermal decomposition of liquid nitromethane. Our results indicate that graphene has almost no influences on the decomposition of nitromethane, hydroxyl-modified graphene acts as an accelerator. Graphyne and its oxygen-containing groups derivatives promote the decomposition process. CH3NO and CH2O are critical intermediates at the initial stage. These observations are helpful for understanding nanocarbon acceleration mechanism on nitromethane thermolysis and for designing novel 2D nanocarbon additives.