Abstract: Beijing’s power system has experienced a significant transition towards decarbonization over the past two decades. Electrification plays a critical role in a lowcarbon power system, as highlighted by the IPCC. This study uses bottom-up data to better understand the rapid electrification and low-carbon transition of Beijing’s power system. We find that the electrification in Beijing has increased by an average of 0.4%/yr from 9.5% in 1995 to 19% in 2019. The unit electricity consumption has decarbonized by 26%, accounting for imports, and by 63% for local generation. With the progress of electrification in Beijing, cleaner electricity plays an increasingly vital role in emission mitigation. We further investigate the driving forces contributing to emission reductions using index decomposition, pair-wise energy flow, and plant-wise power generation data. Results indicate that a fast transition from coal-fired to naturalgas-fired power generation occurred after 2010 and the average emission intensity of local power plants has dropped from 940 tCO2e/GWh in 2000 to 590 tCO2e/GWh in 2015. We predict that Beijing’s electrification will continue to rise to reach above 30% by 2050. The rapid decrease in emission intensity and the evolution of the energy structure demonstrate high efficiency in Beijing’s implementation towards a low-carbon power system.