The main contributions of this work are to study the suitable condition of biogas tri-reforming for DME synthesis process and to design the systems of the biogas tri-reforming process coupling with the DME synthesis. The effects of operating parameters in terms of boundary of carbon formation, steam to carbon ratio, and oxygen to carbon ratio on the biogas reforming process are firstly investigated. To utilize more CO2 in the system, CO2 produced from the DME synthesis is recycled to use in the biogas tri-reforming process. The H-2 and CO yields of the tri-reforming process increase with increasing the CO2 recirculation ratio while the DME yield and system efficiency decrease. The requirement of gas cleaning unit for the DME synthesis coupling with the biogas tri-reforming system is also analyzed. The results indicate that the system with CO2 removal from syngas has more impact on the DME yield than that with H2O removal. On the contrary, the total CO2 emission intensity of the system with H2O removal is lower than that with CO2 removal. When comparing all cases, the system with both H2O and CO2 removals achieves the highest DME yield and system efficiency. (C) 2019 Elsevier Ltd. All rights reserved.