A new method of extracting regional background concentration of CO2 in Yangtze River Delta was established based on the observations of both black carbon concentration and meteorological parameters. The concentrations of CO2 and black carbon were observed at Lin'an regional background station from 2009 to 2011. The regional background concentration of CO2 in Yangtze River Delta was obtained by means of this new method, and the impact of human activities on CO2 concentration in this area was also assessed. The results showed that the regional background concentration of CO2 extracted by this approach was comparable to the values obtained by R statistical filter method, and moreover this new method was better at picking up episodes heavily polluted by anthropogenic emissions. The annual regional average background concentration of CO2 in Yangtze River Delta from 2009 to 2011 was approximately 404.7 ± 8.2 ppm, 405.6 ± 5.3 ppm and 407.0 ± 5.3 ppm, respectively, much higher than global average value, indicating the distinct characteristic of this region. The anthropogenic emissions from Yangtze River Delta had significant influence on the concentration of CO2, increasing the value roughly 9.1 ppm higher than the regional background concentration of this area.