This chapter furnishes an intricate introduction to the emission inventory, model simulation, measure assessment, and the methodology for analyzing “dual attainments” within the research framework. It undertakes an in-depth exploration of the evolution, categorization, data acquisition, and computational techniques employed in emission inventories. Moreover, it outlines the methodology for compiling integrated emission inventories encompassing atmospheric pollutants and greenhouse gases. Central to this discussion is the introduction of a hierarchical emission source classification system, organized into ten anthropogenic emission categories, and further subdivided into sector/industry, fuel/product, combustion/process technology, and end-of-pipe control technology levels. This chapter establishes a dynamic emission characterization model to facilitate a nuanced understanding of emissions dynamics. Leveraging the WRF-CMAQ model, simulations of atmospheric physical and chemical processes are conducted. These simulations, in conjunction with the integrated emission inventory, enable quantitative analysis of emission reduction quantities and the contributions of various mitigation measures, with the goal of supporting the formulation of plans for air quality compliance. Furthermore, this chapter employs the Long Range Energy Alternatives Planning (LEAP) model to scrutinize pathways towards urban peak carbon emissions. It elucidates the foundational assumptions, requisites, and transformations inherent in the LEAP model while constructing a technical roadmap for analyzing trajectories towards peak carbon emissions driven by urban air quality compliance.