This study develops a comprehensive analysis framework and socio-economic energy system model that interlinks demographic change and energy system in order to analyze the urbanization process and its relation with China's long-term CO2 emissions trend as China’ economy enters the “new normal” stage. The results show that, around 300 million people are expected to migrate from rural areas to urban areas by 2050 following a trend, in which people are moving gradually from small and medium city groups to large and super city groups. The migration trend together with the improvement in living standard will promote China's infrastructure construction, industry production, and energy service demand growth. Under the Business as Usual (BAU) scenario, total primary energy consumption in China will reach 8.4 Gtce by 2050, energy-related CO2 emissions will increase to 17.6 Gt, which is 83% higher than the 2013 level. While in the Low Carbon Transition (LCT) scenario with technology innovation, the total primary energy demand for China in 2050 could be controlled at ∼6 Gtce; CO2 emissions would peak during 2020–2025, and be reduced by 78% by 2050 compared to the BAU scenario. In the transition process, non-fossil fuel power generation and energy efficiency technologies have the largest mitigation potentials. Industry and power sectors would peak first before 2020, followed by the building and transport sectors which are projected to peak around 2030. The total additional capital investment required for LCT would account for 1.5% of GDP. Therefore, it is technologically and economically feasible for China to implement new urbanization strategy.