The study of the characteristics of urban greening tree species’ growth and development process is the basis of urban plant community construction, maintenance and management, and ecological function evaluation. Taking the Cinnamomum camphora and Populus × Canadensis ‘I-214’ in the green belt of Jiasongnan Road in Shanghai as the research object, the growth parameters of the two forests were measured respectively in 2010, 2015 and 2020, and the changes in biomass and carbon storage were estimated by single tree allometric growth equation. The results showed that the average DBH of Cinnamomum camphora forest and Populus × Canadensis ‘I-214’ forest increased from 5.71 cm and 10.38 cm in 2010, to 9.69 cm and 15.53 cm in 2015, and 18.14 cm and 24.50 cm in 2020. At the same time, the unit biomass and carbon storage of Cinnamomum camphora forest in 2020 are 4.44 times of 2010 and 1.93 times of 2015, respectively. In 2020, the unit biomass and carbon storage of Populus × Canadensis ‘I-214’ forest were 3.55 times of 2010 and 1.35 times of 2015, respectively. Although the growth rate and biomass of Populus × Canadensis ‘I-214’ increased rapidly, with the passage of time, the development of the Populus × Canadensis ‘I-214’ population tends to weaken, and the growth rate is lower than that of Cinnamomum camphora forest, while Cinnamomum camphora forest shows a sustainable development trend. The results can provide a reference for the rational selection of fast-growing tree species and long-lived tree species and a reference for estimating carbon sink in urban green space.