Achieving carbon neutrality is related to a complex, giant system involving the interwoven coupling and feedback of multiple systems, including nature, society, economy, behavior, technology, and energy. It faces many challenges, such as cross-system and cross-sectoral coupling, subindustry heterogeneity, technology cost dynamics, nonlinearity of technology and behavioral evolution, and social and economic uncertainties. To carry out research on carbon emission technology planning under the constraints of the carbon peak and carbon neutrality targets, it is urgent to develop appropriate methods and models that can depict the connotations of the above challenges. To this end, this research designs and builds a bottom-up national energy technology model (named C3IAM/NET) from the perspective of a complex system, by coupling the whole process, including energy conversion, transportation, end-use consumption, recycling management, and end treatment, and meanwhile coupling the whole industry chain, including raw materials, fuel, production processes, technology, and product/service. Finally, C3IAM/NET model fulfills the goal of production determined by demand, supply-demand interlinkage, and the coordination between technology and economy. C3IAM/NET model provides effective methods and tools for the design of low-carbon transition pathways. The C3IAM/NET model has been successfully applied to the optimization of the carbon peak and carbon neutrality schedule and roadmap for China. The specific action plan for the national carbon emission path is clearly presented here. In addition, this study further provides the carbon emission path and technology layout plan for key industries corresponding to the national carbon peak and carbon neutrality roadmap, such as the iron and steel, cement, nonferrous metals, chemical, and power industries, as well as the building and transportation sectors. This can provide a scientific basis and operational action plan for China to lead and participate in global climate governance.