Abstract: This paper calculates the carbon emissions of road passenger transport in Beijing, and finds out that the carbon emissions of road passenger transport in Beijing grows rapidly from 2005 to 2010, and slightly declines in 2011 compared with 2010 baseline. The increase of daily trips is the main reason for the increase of carbon emissions of road passenger transport in Beijing in the past and future. The decrease in the proportion of both motor vehicles and private cars and the increase in the proportion of public transportation curb the increase of road passenger transport in Beijing. When the daily trips is 40.5 million people, the improvement of the traffic modes'structure will help save 3.024 6 million tons carbon emissions of road passenger transport in Beijing in 2015; And when the daily trips is 44.25 million people, the improvement of the traffic modes' structure will help save 3.304 7 million tons carbon emissions.