Objective To investigate the mechanism of influence of different oxygen concentrations on the composting process of solid biomass waste to determine the optimal oxygen parameters for future controlled ecological life support system(CELSS)solid waste treatment on extraterrestrial planet bases and enhance oxygen utilization efficiency.Methods Using the self-developed solid waste bioreactor test system,aerobic composting experiments were conducted on wheat straw and simulated manure with three different oxygen concentrations of 10%,15%,and 21%.Gas components(O2,NH3,CH4,and N2O)and material maturity indicators(moisture content,dissolved organic carbon,NH4+-N,and seed germination index)were regularly analyzed throughout the treatment process.Results The 15%O2 treatment group had the highest oxygen consumption,the lowest emissions of NH3 and N2O,the best degradation effect of dissolved organic carbon content and the higher NH4+-N content.CH4 emissions in the three treatment groups were all at a low level.At the end of composting,the moisture content of the products in the 10%O2 and 15%O2 treatment groups was all higher than 74%,and the water-holding capacity was the best.The seed germination indexes in the 3 treatment group were 86.64%,123.81%,and 97.98%,respectively.Conclusion Com pared to oxygen concentrations of 10%and 21%,the 15%oxygen concentration can effectively reduce the emission of NH3 and N2O.It also improves nitrogen and water retention,enhances dissolved organic carbon degradation effects,and results in higher maturity levels.