To improve its ability to adapt to climate change, China has promised considerable carbon emission reduction and proposed the policy strategy of “energy revolution”. Considering the lowest carbon emission intensity and the greatest mitigation task in the Eastern Economic Zone of China, this paper analyses the change of carbon emission intensity in Eastern China from 2000 to 2015. First, to prove the significance of carbon emission intensity, this paper studies the cointegration relationship between carbon emissions and the GDP. Afterwards, from the spatiotemporal perspective, this paper decomposes and analyses the carbon emission intensity of the whole country, Eastern China and the provinces of Eastern China and quantifies the impact of different factors. This paper finds that the energy structure of China and the East was in a relatively stable state during this period. In the past, the decrease in carbon emission intensity mainly depended on the improvement of sectoral emission efficiency, and the influence of industrial structure is growing. Furthermore, changes in the eastern region are similar to those in the whole country. The eastern region needs to give full play to its economic advantage in the future. On the spatial scale, GDP per capita and the ratio of tertiary industry have a significant impact on the spatial heterogeneity of carbon emission intensity in East China, while the ratio of secondary industry has few effects. Replacing energy-intensive industry with the service industry will be the focus of emission reduction in the future.