One of the main problems facing the improvement of environmental quality at present is that the two are not addressed together. A unified evaluation system for the co-benefits of reducing carbon emissions and improving the atmosphere is proposed in this study through environmental engineering. Using multiple dimensions and linked quantitative models, the system will combine the help provided by end-of-pipe control technology, structural decarbonization plans, and nature-based engineering solutions. A Synergy Index and an integrated environmental benefit formula are employed to quantify the two objectives in a single analysis system. Based on the above scenarios, the combination of engineering measures for carbon capture and storage (CCS), renewable energy substitution, and sectoral electrification is expected to reduce PM₂.₅ concentrations by as much as 34.6 μg/m³ and prevent about 290–410 premature deaths per million people per year. The above results indicate that the unified framework does outperform the individual-objective optimization of single-measure reductions and provides reference points for policymakers and engineers in their pursuit of carbon neutrality and clean air.