In this work, we performed theoretical investigations into the electronic structure of cyclo-[2n]-carbon molecules with n = 3 ~ 9, by applying both DFT and DMRG methods for comparison purpose. Conclusions can be reached in several angles. Firstly, electron correlation effect is very significant in determining the electronic ground state in cyclo-[2n]-carbon. The bond length alternating phenomenon that exists in all cyclo-[2n]-carbon molecules should be attributed to difference in electron correlation intensity and alternating spatial distribution on neighboring two bonds observed in pairs of bonding and anti-bonding orbitals. Therefore, the dual anti-aromaticity in C16 was suggested to be conceptualized as electron correlation stabilized dual anti-aromaticity. Secondly, C6 has the most