Based on the forest inventory data of Beijing from the seventh (2004-2008),the eighth (2009-2013) and the ninth (2014-2018),the continuous biomass expansion factor method was used to evaluate the dynamic changes of forest carbon stocks in Beijing during 2004-2018,and the carbon tax assessment method was used to estimate the economic value of the forest carbon sink in Beijing from 2004 to 2018. The results showed that: the forest carbon storage in Beijing was 7.09Tg from 2004 to 2008,9.43Tg from 2009 to 2013,and 15.39Tg from 2014 to 2018. The forest carbon density was 19.94,21.97,and 24.75t/hm2,respectively. The young forest accounted for the highest proportion of total carbon storage,accounting for 52.04%,47.64% and 53.42% in the three inventory periods respectively,while middle forest accounted for 23.05%,24.78% and 21.00% in the same period respectively. The economic value of forest biomass carbon sink in Beijing was 5.075 billion yuan between 2004 to 2008,5.725 billion yuan between 2009 to 2013,and 7.652 billion yuan between 2014 to 2018,the annual increment of economic value of forest biomass carbon sink in 15 years was 171.8 million yuan. The carbon stocks and carbon stock economic value of the forest resources in Beijing showed an increasing trend,but the proportion of young forest and middle forest was relatively high,and the carbon density of forests was low,so the scientific cultivation and management of the forest should be strengthened in order to continuously improve the function and value of the forest carbon sink.