A mesoporous activated carbon (AC) can be successfully prepared by catalytic activa-tion with carbon dioxide. For iron oxide as catalyst, there were two regions of mesopore size distribution, i.e. 2-5nm and 30-70nm. When copper oxide or magnesium oxide coexisted with iron oxide as composite catalyst, the content of pores with sizes of 2-5nm was decreased, while the pores with 30-70nm were increased significantly. For comparison, AC reactivated by carbon dioxide directly was also investigated. It was shown that the size of mesopores of the resulting AC concentrated in 2-5nm with less volume. The adsorption of Congo red was tested to evaluate the property of the result-ing AC. Furthermore, the factors affecting pore size distribution and the possibility of mesopore formation were discussed. A mesoporous activated carbon (AC) can be successfully prepared by catalytic activa tion with carbon dioxide. For iron oxide as catalyst, there were two regions of mesopore size distribution, ie 2-5 nm and 30-70 nm. When copper oxide or magnesium oxide It was shown that the coexisted with iron oxide as composite catalyst, the content of pores with sizes of 2-5 nm was decreased, while the pores with 30-70 nm were increased significantly. size of mesopores of the resulting AC concentrated in 2-5 nm with less volume. The adsorption of Congo red was tested to evaluate the property of the result-ing AC. Furthermore, the factors affecting pore size distribution and the possibility of mesopore formation were discussed .