Due to the toxicity and low mass transfer of CO, its efficient conversion is crucial for syngas biomethanation. In the present study, anaerobic co-digestion of CO and carbohydrate-rich synthetic wastewater was conducted to facilitate the CO conversion performance, followed by microbial analysis with and without methanogenic activity inhibition (namely, digestion and acidification systems). The results indicated that glucose addition in co-digestion system dramatically enhanced CO consumption. The maximum consumption rate (μ-max) of CO increased by about 65 % with adding glucose. However, CO presented partial inhibition on methanogenic activity without declining methane yield. Microbial analysis showed that microbial diversity increased in co-digestion systems. Hydrogenotrophic methanogens from Methanobrevibacter became dominant in all individual and co-digested systems. Methanogenic activity inhibited community proved the bacteria mainly mediated CO conversion, and glucose addition promoted the growth of acetogenic bacteria from Firmicutes, relating to the enhancement in CO consumption. Species from Synergistota worked as the main syntrophic oxidizers, along with Defluviitoga, Syntrophomonas, and Syntrophaceticus, assisting methane production by hydrogenotrophic methanogens. The outcomes in the present study supply an efficient strategy for synergetic treatment of syngas (CO-rich gas) and organic waste/wastewater for energy recovery.