China's greenhouse gas (GHG) emissions are projected to peak by 2030 and China makes great efforts to reach the peak as soon as possible. As the 'frontier' of Chinese Reform and Opening-up, Beijing has set a goal in 13th Five-Year Plan that local GHG emissions will peak by 2020. This research analyzes the situations of socio-economic development and energy consumption in Beijing and establishes LEAP-Beijing model for the medium to-long-term prediction of GHG emissions. The energy demand module in LEAP model has six branches, including civilian sector, agriculture, industry, construction industry, transportation and service sector. The analysis and evaluation of their potentials to cut emissions and the difficulties to implement can help Beijing determine the development priority and take right measures to develop a low-carbon society. Four scenarios are set in LEAP-Beijing model, including Business-As-Usual scenario (BAU), Low-Carbon scenario (LC), Enhanced Low-Carbon scenario (ELC) and Peak-Reaching scenario (PR). These scenarios are applied to analyze the total amount of GHG emissions in Beijing and how the peak-reaching time varies due to the impacts of different policies.