This chapter elaborates on three socioeconomic models under the C3IAM framework: C3IAM/EcOp, C3IAM/GEEPA, and C3IAM/MR.CEEPA. C3IAM/EcOp, based on optimal economic growth theory, integrates economic and climate modules to internalize climate change into long-term macroeconomic analysis, quantifying the impacts of mitigation costs and climate damage on growth while coordinating regional actions through dynamic game mechanisms. C3IAM/GEEPA and C3IAM/MR.CEEPA are computable general equilibrium models encompassing production, income-expenditure, trade, investment, and emission modules. They support multiregional (global and Chinese provincial) policy simulations, balancing government regulation with market mechanisms to assess direct and indirect economic effects of emission reduction policies. The socioeconomic models provide scientific foundations for global climate governance, regional mitigation strategies, and industrial layout optimization, facilitating synergy between short- and long-term emission reduction goals.