Molybdovanadophosphoric heteropolyacids have been employed as anode electron carriers for coupling pretreatment of wheat straw and direct conversion of the biomass to electricity, which can provide a new idea for lignocellulose conversion to energy. • Molybdovanadophosphoric heteropolyacids as anode electron transfer carriers. • Coupling biomass pretreatment and direct biomass-to-electricity conversion. • Cellulose enzymatic digestibility was well improved. • Electricity co-generation by re-oxidization of the electron carriers. • Pretreatment as the “charging” process. • Re-oxidation of electron carriers as the “discharging” process. Owing to their acidity, oxidizing ability and redox reversibility, molybdovanadophosphoric heteropolyacids (H n +3 PMo 12- n V n O 40 , abbreviated as PMo 12- n V n ) were employed as electron transfer carriers for coupling biomass pretreatment for enzymatic hydrolysis and direct biomass-to-electricity conversion. In this novel coupled process, PMo 12- n V n pretreatment that causes deconstruction of cell wall structure with PMo 12- n V n being simultaneously reduced can be considered as the “charging” process. The reduced PMo 12- n V n are further re-oxidized with release of electrons in a liquid flow fuel cell (LFFC) to generate electricity is the “discharging” process. Several Keggin-type PMo 12- n V n with different degree of vanadium substitution (DS V , namely n ) were prepared. Compared to Keggin-type phosphomolybdic acid (PMo 12 ), PMo 12- n V n ( n = 1–6) showed higher oxidizing ability but poorer redox reversibility. The cellulose enzymatic digestibility of PMo 12- n V n pretreated wheat straw generally decreased with increase in DS V , but xylan enzymatic digestibility generally increased with DS V . PMo 12 pretreatment of wheat straw at 120 °C obtained the highest enzymatic glucan conversion (EGC) reaching 95%, followed by PMo 11 V 1 pretreatment (85%). Discharging of the reduced heteropolyacids in LFFC showed that vanadium substitution could improve the maximum output power density ( P max ). The highest P max was obtained by PMo 9 V 3 (44.7 mW/cm 2 ) when FeCl 3 was used as a cathode electron carrier, while PMo 12 achieved the lowest P max (27.4 mW/cm 2 ). All the heteropolyacids showed good electrode Faraday efficiency (>95%) and cell discharging efficiency (>93%). The energy efficiency of the coupled process based on the heat values of the products and generated electric energy was in the range of 18%–25% depending on DS V . PMo 12 and PMo 11 V 1 seem to be the most suitable heteropolyacids to mediate the coupled process.