Cities are key to global greenhouse gas emissions management. To explore urban greenhouse gas peak pathways, a city-level Energy Consumption and Greenhouse Gas Emission Analysis model was developed by using Long-range Energy Alternatives Planning model framework. Using the city of Guangzhou as a case study, this research compiled a overall energy balance sheet of base year and simulated future CO2 emission trends from 2015 to 2030 under three scenarios. Results show that CO2 emissions in Guangzhou will peak around 2023 under the current policy scenario. In order to advance the CO2 emissions peak to 2020, the more stringent emissions-reduction policies and measures need to be adopted under the peaking scenario and enhanced peaking scenario, with the peak emission value of 125–127 Mt CO2e. The industrial sector is the only sector in which CO2 emissions have peaked in Guangzhou, the building sector’s CO2 emissions will not peak by 2030 under any of the three scenarios, while the transportation sector, which will contribute 50 percent of emission reduction potential, is the key to achieve its goal of peaking CO2 emissions on time. In the short term, stringent reduction strategies on the transportation, industrial, and power sectors are needed, including transport mode adjustment, industrial structure adjustment, electrification level improvement, clean-up transformation of thermal power, and energy efficiency improvement. However, in the long term, reduction strategies for the building sector, like energy efficiency improvement and large-scale application of renewable energy, will be essential for Guangzhou.