The azepine- and oxepine-embedded polycyclic aromatic hydrocarbons (PAH) 1–3, as the hexa-peri-hexabenzocoronene (HBC)-based nanographenes (NG) were designed and synthesized by Diels–Alder reaction of cyclic alkene with tetrachlorothiopheneS,S-dioxide, followed by Suzuki–Miyaura cross-coupling and Scholltype cyclodehydrogenation. Due to the strained seven-membered ring and the inherent structural pattern, heteroatom-doped NGs 1–3 show Cs symmetrical, double saddle-helix hybrid conformation, which represents a new shape for HBC-based nanographenes. The calculation studies reveal the low aromaticity of the 8π heterocycles themselves and the heterocycles also decrease the electron delocalization of benzenes surrounding them. Dynamics-based calculation suggests the C s symmetry would maintain druing the dynamics process. Meanwhile, we show the property perturbation by doping with different heteroatoms.