To investigate iron enhanced anaerobic digestion performance, a survey was conducted to examine how iron powder (IP) affected the stability of a co-digestion reactor for kitchen waste and Pennisetum hybrid in a semi-continuous mode. In addition, the mechanisms underlying this process were analyzed according to various parameters and microbial communities. The results showed that the maximum stable operational organic loading rate (OLR) for the IP reactor increased by 50% compared to that of the control reactor, while the specific methane yields and volumetric methane yields increased by 4.8%-106.8% and 6.3%-105.9%, respectively, when OLRs were 1.0-3.0g VS/ (L.d). Meanwhile, selective enrichment of propionate-utilizing bacteria and hydrogenotrophic methanogens may have promoted the conversion of volatile fatty acids while increasing gene abundance via a methane-forming pathway. The addition of IP changed the dominant microorganisms related to the methanogenesis pathway. Additionally, the occurrence of interspecies formate transfer promoted anaerobic digestion stability in the IP reactor. All rights reserved, Elsevier.