Cyclo[16]carbon is the first antiaromatic all-carbon ring discovered in recent experiments. We studied its thermal stability and found that cyclo[16]carbon showed poor thermal stability. Subsequently, we studied its bonding properties, electron delocalization and antiaromaticity by quantum chemical calculation and wave function analysis. We observe that cyclo[16]carbon is a doubly antiaromatic system with alternating long and short bonds, where the shorter C-C bond has stronger π interactions and delocalization. In addition, by studying electron spectra and nonlinear optics, we elucidating the contribution of in-plane and out-of-plane π (πin and πout) orbitals to electron excitation, and confirming the nonlinear anisotropy of cyclo[16]carbon. Electrostatic potential (ESP) and local mean ionization energy (ALIE) analyses demonstrate the electrophilic properties of the short C-C bond. Our comprehensive characterization of cyclo[16]carbon will enable researchers to deepen their understanding of cyclo[16]carbon and thus derive its more valuable structure.