Carbon sequestration capacity is the key factor in maintaining biodiversity and ecosystem services. However, further research is required on how to evaluate the impact of protected areas on carbon sequestration capacity from a global scale. To date, we propose a carbon density index of global protected areas (>10 km, 32,756 samples) by the Integrated Valuation of Ecosystem Services and Trad'eoffs carbon model over the period 1994-2015. Then, we use the propensity score matching and difference-in-difference methods to separate the time effect and policy effect of the construction of protected areas on carbon sequestration capacity. Our analysis reveals that the carbon sequestration capacity can be improved by 0.39% by constructing global protected areas. There are regional differences with carbon sequestration capacity improvement globally. Africa has the largest value of increased carbon sequestration capacity, followed by Asia, Oceania and Europe. Upgrading protected areas (0.05%), strictly implementing planning (0.18%) and enhancing the power of local governments (0.08%) are conducive to improving carbon sequestration capacity. The assessment of the carbon sequestration capacity dynamic with protected areas is of great significance to meet the Convention on Biological Diversity.